Gunman Derrick Bird's rampage across west Cumbria left 12 people dead and 11 injured.
He later turned the gun on himself, as armed police pursued him to woodland near the village of Boot.
Here is a summary of how events unfolded:
Kevin Clarkson, deputy chief executive of West Cumberland Hospital, says three of the injured being treated there are in a critical condition. Five more patients are in a serious condition.
Sixty-six-year-old Jane Robinson has been named as another of the victims, the Press Association is reporting. A family friend confirmed the news a short time ago. Ms Robinson was shot in Drigg Road just yards from the home she shared with her twin sister Barrie.
Home Secretary Theresa May said the events in Cumbria were "very serious and tragic". She said she would not comment on the details of the police investigation, but would make a statement in the House of Commons on Thursday.
Deputy chief constable Stuart Hyde said two weapons had been used in the shooting spree. But he said: "While this was a terrifying and horrific incident, it is by its nature very unusual, both locally, regionally and nationally. Cumbria prides itself on being a safe place to work, play and to enjoy life."
But local MP Jamie Reed said the community around Whitehaven was "the kind of place where you can leave your door open, so it's the kind of thing that really does shake the very foundations".
Shooting victim Garry Purdham was "quite simply a gentleman and a pleasure to know". So said David Bowden, chairman of Workington Town Rugby League Club, where Mr Purdham played in his spare time. The victim's brother, Rob Purdham, is the captain of Harlequins Rugby League side and has been capped five times for England.
Two of the victims of the shooting have been named locally as Darren Rewcastle and Garry Purdham. Mr Rewcastle was a taxi driver. Mr Purdham was a farmer's son and is believed to have had two young children.
"We are still at a very early stage in our investigation and we are not able to really understand the motivation behind it - or establish whether this was a premeditated or random attack," says Deputy Chief Constable Stuart Hyde. He says officers are now investigating Derrick Bird's history and his access to firearms, and are trying to understand "why someone would want to take so many lives in such a short space of time".
Twenty five people are injured, three critically, says Dr Nigel Calvert, associate director of public health from NHS Cumbria. He says specialist support services will be set up in the county to help those affected by what happened.
Deputy chief constable Stuart Hyde says the force is dealing with 30 separate crime scenes. He confirms that the body found in woodland was that of Derrick Bird and that he appeared to have shot himself.
Deputy chief constable Stuart Hyde tells a press conference that 12 people have been shot dead as well as Bird. He describes the day's events as "horrific".
One man is believed to have been shot dead on a bridge in the village of Egremont. Neighbour Tracy Maudling said: "For him to lose his life like that is terrible. He was just a quiet man. We all go up the street every day, he was just in the wrong place at the wrong time."
A taxi driver with Gosforth Taxis, who asked not to be named, told the Press Association: "It's total carnage. I was in Whitehaven this morning, I heard the first shots and the next thing you know police were here, there and everywhere."
Residents in Derrick Bird's home village of Rowrah told the Press Association he had two grown-up sons, one of who became a father for the first time only two weeks ago.
Ryan Dempsey, 26, who lived two doors away from him, said: "I have known him for 15 years. He was always pleasant, always had time to say hello. As far as I'm concerned this is completely out of character. I had never seen him in a bad mood."
Billy Boakes, from the village of Egremont, said a woman had been shot dead outside his home. "She was just on the pavement with a couple of shopping bags in her hand," he told the Press Association.
Mr Boakes said witnesses had later told him what happened: "He stopped his car, got out the car, got his gun out, went up to her and just shot her in the stomach."
A North West Ambulance spokesman says they received 51 emergency calls during the three-and-a-half hours that the shooting incident was taking place.
A friend of Derrick Bird's, Peter Leder, told CNN he was "an outgoing, well-known guy, who everyone liked", but when they spoke on Tuesday night, Mr Bird told him: "You won't see me again."
Michelle Haigh, the landlady of Derrick Bird's local pub, said he was "a nice guy, nothing out of the ordinary". She said no-one she had spoken to could think of any trigger for Wednesday's events.
Police say reports that Derrick Bird's mother was among those shot are incorrect. They say she is alive and is being supported by her family.
Eyewitness Barrie Moss tells the BBC he was cycling home when he saw the gunman beside a car with what looked like "a huge sniper rifle". At first, he said, he thought it was a toy but then the man drove off leaving behind a dying woman.
Mr Moss and another man did their best to save the woman, who had been shot, but she died in their arms.
The BBC's Chris Stewart, in Whitehaven, says he understands there are more than five fatalities.
The BBC News Channel's chief political correspondent Laura Kuenssberg says Home Secretary Theresa May will make a full statement to the Commons on the shootings on Thursday. Our correspondent says the government doesn't know yet whether Derrick Bird was a licensed gun holder.
A farmer believed to have been killed in his field in Gosforth was in his early 30s with two young children, a local resident said. The neighbour told the Press Association she had heard that the victim was trimming hedges with his uncle when the gunman drove past, wound down the car window and shot him.
Rod Davies, landlord of the Gosforth Hall Inn in the village of Gosforth, said he understood the gunman had shot his own mother. Mr Davies told the Press Association: "The guy flipped for whatever reason. Whether it was pre-meditated, we don't know."
At least five people have died and at least 25 have been injured in the shootings, police say. Officers are now working to identify those who have died and inform immediate family.
Police repeated their helpline number - 0800 0960095 - and appealed for members of the public with friends and family in the West Cumbria area to ensure they are safe and well.
Rev John Bannister, from the Whitehaven parish, tells the BBC it is "a day of shock and trauma" for the community. He says there is a feeling of "disbelief" that something like this could happen there.
Sue Matthews, a telephonist at A2B Taxis in Whitehaven, said Derrick Bird was "a quiet fellow". She told the Press Association: "I am in absolute shock. I can't believe he would do that. I know him through work, he was self-employed, but it's a small place. I know he had one son, who was grown up, and he lived alone."
Ms Matthews said he was "fairly popular", adding: "He was known as Birdy."
Labour MP for Whitehaven Jamie Reed says the community was "already grieving" following a fatal coach crash last week which killed three people.
"The community's already feeling very, very sore, very battered, and for something like this to happen in an area of exceptionally low crime, one of the lowest crime rates in the country, is a huge shock to the system for everybody."
Prime Minister David Cameron tells the House of Commons that at least five people have died in the Cumbria shootings. He says the thoughts of all MPs are with those affected by these "shocking" events.
The BBC understands that police are still searching for casualties along the route taken by Derrick Bird.
NHS Cumbria say all routine operations have been cancelled at West Cumbria Hospital in Whitehaven.
Julian Kirkley, a resident in the village of Frizington, told the BBC his next-door neighbour knew suspected gunman Derrick Bird. "She's lived here all her life and knows the Bird family very well," he said. "She's completely surprised and said Derrick Bird seemed a very normal person."
A major incident has been declared at West Cumberland Hospital in Whitehaven. The accident and emergency department at the Cumberland Infirmary in Carlisle is also ready and also on full incident stand-by.
Referring to a coach crash last month in Cumbria in which two teenagers and and a 68-year-old man died, trust deputy chief executive Kevin Clarkson said: "This is our second major incident within 10 days and again our staff are doing a fantastic job under very difficult circumstances."
The hospital did not confirm specific casualty numbers.
Police are appealing for anyone who witnessed any of the events of today to come forward. They also want anyone who knows of Derrick Bird's whereabouts in the past 24 hours to contact them.
Whitehaven councillor John Kane tells the BBC that Derrick Bird had always appeared to be "very placid... a very quiet man... kept himself to himself". He says "something must have pushed him over the edge".
The BBC's Chris Stewart, in Whitehaven, says Derrick Bird is believed to have shot himself dead.
Police had previously warned the public to lock themselves indoors while the incident was ongoing. They now say those who were sheltering can safely return to their to normal activities.
Police say they have seized a gun from the scene where Derrick Bird's body is believed to have been discovered. They say they are now working to confirm the number of people injured or dead.
A helpline number 0800 0960095 has been set up for anyone concerned about relatives.
Police hunting Derrick Bird say they believe they have found his body in a wood near the village of Boot.
The BBC's Daniel Sandford says he has heard reports that several victims have been shot in the face.
An eyewitness in the village of Boot tells the BBC they saw Derrick Bird crash the car he was driving. He then made off on foot.
John Cook, from Seascale, tells the BBC he saw three dead bodies on a single street in the village. "I thought a person had just collapsed. Then I went another 50, 60 or 70 yards further on and saw a cyclist. It looked as if something had happened to them, there was a blanket over that person."
Dr Barrie Walker, a GP in the village of Seascale, tells the BBC he personally certified two people dead. Both had suffered shotgun wounds. He describes the experience as "horrific".
The BBC's Chris Stewart, in Whitehaven, says he understands there have been 11 shootings - it is currently unclear how many of those have been fatal.
Cumbria Police say they are using every armed police patrol in the county to apprehend Derrick Bird. They say the response includes armed vehicle and foot patrols, police dogs units and air support from Lancashire. He is currently believed to be in the Boot area in Eskdale Valley.
Sean King, landlord of the Boot Inn, says about 25 people, including several "shell-shocked" tourists, are currently "holed up" in his pub. He tells the BBC helicopters are involved in the search for Derrick Bird, some so low that they are "literally shaking the rafters of the building".
Sellafield nuclear plant, close to the village of Seascale where there is thought have been some shooting earlier, is in lockdown. All gates to the site have been closed. Morning shift personnel will remain on site and afternoon shift staff have been advised not to turn up for work until further notice.
Deputy chief constable Stuart Hyde tells the BBC that public safety is the force's number one priority at this time. He says there have been a number of fatalities and injuries. He repeats the message that members of the public should stay indoors.
The BBC understands that Derrick Bird is a taxi driver. A man who knows him says he is self-employed and he "wouldn't have expected him to do something like that".
The BBC's Chris Stewart, in Whitehaven, says a farmer is understood to have been shot dead at point blank range in a field at 1130 BST near the village of Gosforth.
Police say Derrick Bird has abandoned his car in the Boot area and is now believed to be travelling by foot. Officers are in pursuit and urge members of the public to shelter indoors until further notice.
Officers are also asking walkers and tourists in that area to be vigilant, take extra care and head indoors if at all possible. Drivers are being warned not to pick up hitchhikers.
Radio Cumbria reports that at least four people are feared dead.
Police release a photograph of the man they are searching for - 52-year-old Derrick Bird, of Rowrah near Frizington. He was last seen heading south in the Central Lakes direction. He may have abandoned the car and be proceeding on foot.
Police also confirms there have been "a number of fatalities" and they are working to identify the individuals and inform relatives.
Police say armed officers are working to apprehend a man who is described as in his thirties with a shaven head, and driving a dark grey/silver Citroen Picasso registration ND55 ZFC. Any members of the public who see the vehicle are asked to call 999 immediately.
Police confirm that a number of people have been injured after shots were fired in the Whitehaven, Seascale and Egremont areas. They ask people in the Millom, Broughton, Central Lakes and West Lakes areas to stay indoors and tune in to local radio to stay up to date on the latest situation.
One person is known to have been shot dead in the town of Whitehaven. The shooting is understood to have taken place in Duke Street at 1035 BST.
Cumbria Police say officers were called to Duke Street in Whitehaven at 1035 BST after reports that shots were fired by a man. Armed police are working to apprehend the man and are asking members of the public in Whitehaven and Egremont to stay indoors until further notice. The man is believed to be driving a silver/grey Citroen Picasso car.