John Grier was "rag-dolled" on the back axle of the heavy goods vehicle after it drove over him and his wife Emma.
The Griers, who were both 76 and from Motherwell, North Lanarkshire, had been crossing a busy road when they were struck by the lorry and dragged along the road.
A trial at Hamilton Sheriff Court has heard horrified eyewitnesses describe how they saw the Griers being fatally injured in the town in January, 2011. Lorry driver John Campbell, 66, of Glasgow, denies causing their deaths by driving without due care or attention.
Under questioning from Natalie Henderson, prosecuting, Simon Steel, 36, who was in a car with his wife told how she had screamed as Mr Grier was trapped by the truck's wheels.
Mr Steel, an ex-Army medical officer, said: "We were going to Coatbridge because one of the kids needed to see a doctor.
"We were running late so my wife asked me to go into her bag which was at my feet and phone the surgery and say we would be a few minutes late. I was looking through my wife's bag for her phone and my head was facing down.
"She suddenly started screaming, her scream was just out of pure terror and horror at what was happening.
"I looked up from the bag and just saw a man going round the back wheel of the lorry and a woman also going under it.
"The man was being rag-dolled round the back axle of the vehicle."
Mr Steel then told how he had given medical assistance to the stricken Mr Griers and how Mrs Grier had asked after her husband, who was known as Jake, as she lay injured.
He said: "I jumped out of the car and immediately phoned 999.
"I went across to try and help them in any way I could before the paramedics and ambulances arrived.
"When they did arrive I told them straight away that as far as I was concerned Jake was the priority casualty for them given what I saw happen to him.
"I then left Jake and went up to Emma who was lying further up the hill.
"She eventually regained consciousness and the first thing she asked me was, 'How's my Jake?' That is the first time I knew his name.
"Other paramedics then began to assist her."
Simon Collins, defending, asked Mr Steel if he had seen the truck driver's face during the incident. He said: "No. I was only looking at what was happening to the couple, I didn't look at the driver."
Witness Craig Barber, 34, said Mr Grier had banged on the front of the truck to try to get it to stop moments before it went over the top of him and his wife.
He said: "I saw the elderly gent put his hands up and strike the front of the truck two or three times before he fell back. When he fell he tried to push his wife out of the way which made her fall and the lorry went over the top of them both.
"As it happened I was shouting 'stop, stop' when the lorry moved.
"The lorry did stop eventually and I got out my car and called 999."
Margaret Gallagher, 43, described how she heard the couple shout out before they were run over.
She said: "I heard them screaming very loudly just before the man went under the wheel. I ran out of my car and left the engine running, I tried to help them when the lorry eventually stopped.
"The driver was crying and very distraught by what had happened."
The trial, before Sheriff Joyce Powrie, continues.