The Omagh Bombing Inquiry is examining whether the single worst atrocity of the Troubles could have been prevented
Twenty-nine people, including a woman expecting twins, were murdered in the Real IRA attack on 15 August 1998
This is the fourth week of hearings
Edited by Conor Neeson. Warning: This page contains distressing details
Mr Marshall says the right level of professional help was not available.
"Those nurses were wonderful people and great people but they were not even psychiatric nurses they were just ordinary nurses," he says.
"And we needed help far beyond their abilities."
He says that his officers attended some of the funerals of the deceased "but you couldn't get to them all".
But he says this had a "really adverse affect on some of the younger members of the crew with no real professional help".
He said these officers were coming to him and "pouring their hearts off".
He confirms that the normal response was to "man up and take a stiff drink".
Mr Marshall recalls the feelings of exhaustion he experienced while having to identify the bodies.
"It was like a double whammy, you came out of the hell of that scene for five hours," he says.
"You didn't think you would have to do that, but, we did it."
He says his officers were then asked to help identify the dead.
He says that his team were "emotionally exhausted" and doing this task on your own "wasn't going to work".
He says he decided that they would do each together as a group.
When Mr Marshall arrived at the mortuary, he was struck by what his constables had been through.
"Their adrenaline had started to dump," he says.
"The enormity of what they had been through and what they had seen had started to hit them.
"They looked terrible," he adds, "covered in blood and debris and dirt... a sorry looking sight."
Mr Marshall says that after supervising the transport of bodies to the army barracks he left the scene.
He says there was only "one hiccup" when one of ambulance crews arrived before turning and walking away saying "sorry we just can't handle this".
But he says they "got everyone out".
When the ambulances arrived, Mr Marshall says: "We were able to start allocating bodies and their 'body constable' to the mortuary."
The temporary mortuary was set up because the official "local mortuary could not deal with this".
He says that he had a police radio and there was a channel dedicated to him to give updates.
He says he found this "really difficult" and choked up with emotion providing this information.
He says when he said the numbers they would ask him to repeat because they "couldn't fathom" the numbers.
Mr Marshall says he instructed the constables to place the deceased in a clothes shop.
To his day, he says he is still unable to enter the alleyway.
He says he envisions himself walking between the dead.
"I've never been back," he adds.
Mr Marshall says that an officer came to tell them that Market Street Arcade was now full of bodies.
He said that this didn't really register with him so he went to look and found the alleyway "jammed with dead, and there was blood everywhere".
"Basically we just couldn't fit anymore in."
Mr Marshall says he instructed a constable to get some pen and paper and record everytime he allocated a body to a constable.
He would then use a bit of paper to attach to one of the bodies allocated.
Mr Marshall selected six constables who would be his "body team".
He says the bodies of the dead were wrapped in curtains and bedsheets.
He says the bodies were then moved "to get them away form the lenses of the press".
The bodies were moved to Market Street Arcade.
He says he knew the scene of the bombing would have to be sealed off.
"The only way I could get everybody's attention was to stand in the middle of the road and scream my head off."
He says he moved people off the road and instructed officers to seal the road off with tape.
He says despite the risk that the buildings could collapse all his officers stayed at the scene.
As more senior officers arrived at the scene, it was determined that Mr Marshall should "carry on and continue at the scene."
After which he remained in command of the scene, for five hours.
Mr Marshall now talks of the support that his wife has given to him, describing her as his "rock".
"I know she's had to deal with a lot for all the things I've been through."
He says she had stuck by him and that he'll forever be in her debt.
He recalls: "I saw a young infant, lying in the window.
"I was standing there looking at her and she looked so peaceful.
"But at that time, I didn't know where my wife and daughter were and my daughter was the same age."
He said he stood and wondered if it was his daughter.
At this point he felt something "nudge his leg" and when we looked down it was another body, which had "floated into me".
He says there was a shortage of vehicles to transport people to hospital
"We just stopped whatever cars we could."
He says the manger of Ulsterbus came down to the scene and organised for a bus to come and help transport in injured.
Mr Marshall said "I badly needed a doctor at the scene.
"Because only a doctor can declare someone officially dead.
"I noticed someone with a fluorescent jacket with the word doctor on the back."
Mr Marshall said he "grabbed the hold of him and asked him to go around everyone now and put a stethoscope on them" to "pronounce life extinct".
He said the doctor wondered why he wanted him to put a stethoscope on bodies which no longer "had the limbs to preserve life".
He says his officers were "just ordinary young men with mums and dads and brothers and sisters, who I was demanding carry out extraordinary tasks".
He adds that he "to this day" has an "immense pride in them all".
Mr Marshall recalls seeing one of his officers cradling a young woman.
He says he noticed that the young officer was herself traumatised.
He says he instructed her to take the woman to hospital and thus remove herself from the horror.
He says looking back it occurs to him how young some of the officers were.
"They were just kids."