Two women have been shot dead at a house in East Sussex, police have said.
Armed officers responded to reports of a shooting in Bexhill Road, St Leonards, at 19:43 GMT on Friday.
Sussex Police said two women, aged 32 and 53, were killed. Two more women - one of whom was pregnant - were taken to hospital suffering from shock.
Two hours later, a 35-year-old man was arrested on suspicion of murder and a firearm was seized.
Ch Supt Jason Taylor said the women - who were known to the suspect - died at the scene.
He added: "Two other women, who were also at the house, were helped to safety. They are being supported by specially-trained officers."
Insp Mark Rosser tweeted about "one of the worst shifts in 25 years" and said the Met Police was called in to help.
That has got to be 1 of the worst shifts I've had in 25 years service, some gr8 work by my team dealing with a horrendous crime, a number of scenes, 30 plus displaced families & all the other usual business - thks to @metpoliceuk Trojan support. Thoughts are with those involved.— Inspector Mark Rosser (@Insp_Rosser) March 17, 2018
Armed police cordoned off Bexhill Road and surrounding streets following the shooting and some families were asked to leave their homes as officers searched for the suspect.
Bexhill Road has now re-opened and residents have been able to return to their homes, Sussex Police said.
Officers from the Surrey and Sussex major incident team are leading the investigation into the deaths.
Det Ch Supt Jason Tingley said: "Tragically two women aged 32 and 53 have died after being shot and our thoughts are with their family and friends.
"We are not looking for anyone else in connection with this incident but we are appealing for any witnesses to come forward."
At the scene: BBC reporter Charlotte Wright
There's still significant disruption as a large part of the road is cordoned off and traffic and pedestrians are being diverted.
Neighbours in nearby houses have expressed their shock at what happened. Many tell me it's a quiet area with no trouble.
Meanwhile, behind the police tape officers and forensics continue to work at the scene, gathering evidence to piece together the events of Friday night.
The investigation continues here in the flurries of snow and freezing cold temperatures.
Home Secretary Amber Rudd, who is also MP for Hastings and Rye, tweeted her sympathy to the family and friends of the victims.
1/2 My thoughts and prayers are with the family and friends of the victims in last night's tragic shooting incident in Bexhill Road. I've spoken to the police chief and want to commend the swift actions of the police and other emergency services in responding to this incident.— Amber Rudd MP (@AmberRuddHR) March 17, 2018
Matthew Beaver, Conservative councillor for West St Leonards, told BBC Sussex: "There is a great community spirit amongst the residents of West St Leonards, which I know will continue to be shown in the coming days helping out the friends and families of the victims and helping out those in the wider community."