A recovery driver killed a woman as he was too busy checking his mobile phone, a court has heard.
David Shields, 34, crashed into Yvonne Blackman's car in a line of traffic on the A75 in Dumfries last February.
At the High Court in Glasgow he admitted a charge of causing the mother-of-four's death by dangerous driving.
Footage captured Shields focusing on his phone for a full 18 seconds in the lead-up to the fatal crash.
Ms Blackman, 66, never recovered and died weeks later in hospital.
Shields, who had a previous conviction for speeding, was remanded in custody pending sentencing next month.
Ms Blackman, of Lockerbie, Dumfries and Galloway, was on her way to meet friends to carry out missionary work when she was killed.
She ended up getting caught in heavy traffic on the A75 Gretna to Stranraer road about 08:30 on 8 February 2017.
The court heard Shields was driving in the area while working for 911 Rescue Recovery.
He met the same line of traffic before ploughing into the back of Ms Blackman's Toyota Yaris.
Prosecutor Liam Ewing said: "Witnesses noted that the lorry did not appear to brake until a short distance before the collision, at which time it skidded or snaked."
Ms Blackman's car hit a BMW in front before spinning to a halt.
The pensioner was discovered unconscious as Shields got out of his truck.
He was found "sobbing" at the side of the road.
Mr Ewing: "He stated he had left Stoke and was driving to Kilmarnock.
"He did not say what caused the collision."
Ms Blackman was taken to hospital with a serious spinal injury and multiple rib fractures.
The court was told she passed away on 23 February.
The cause of death was chest and spinal injuries due to the crash.
Shields, of Drongan, East Ayrshire, was later questioned by police.
He initially claimed he had noticed "at the last second" that the "traffic was not moving".
Shields went on: "There were no brake or hazard lights on the vehicle in front. I slammed the brakes on, slid and collided."
Crash investigators later stated Shields had a potential distance of 256 metres to stop his vehicle and avoid the smash.
This was deemed "sufficient" to spot any car ahead.
'Focusing on phone'
But, study of the seven cameras in his truck's cab showed his "attention had been on a dash-mounted mobile telephone".
Mr Ewing said: "An analysis established he had been focusing on the phone...therefore failing to maintain proper observations of the road ahead.
"(This was) for a period of 18 seconds prior to reacting to the presence of the car."
The footage was shown in court and Shields appeared to break down in the dock as it was played.
He is seen driving while checking the phone before his cab shudders as it hits Ms Blackman's car.
It is not known what he was doing on the mobile at the time.
Part of the charge Shields pled guilty to stated he did "repeatedly interact with and focus your attention" on a phone.
His QC John Scullion said: "He accepts full responsibility for the death and bitterly regrets driving as he did."
Lady Stacey banned him from the road meantime as sentencing was deferred for reports.