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
He says he saw "vast numbers of people who were seriously injured and people who were obviously dead".
He adds it kept getting worse.
He says he tried to allocate police to people who were injured and dying.
Mr Marshall remembers how people were helping with the rescue operations, "taking instruction" and "doing a sterling job".
"I ordered people, my own constables and members of the public to get everything they could get their hands on to soak up blood.
"We also took a lot of curtains to transport people."
He recalls going to the engine block of the car that contained the bomb and that people were trapped and burning to death.
He says the screams are "one of my nightmares".
He says a member of the public appeared with a fire extinguisher before they lifted the engine block to slide people out.
He says most of those people survived, but one did not.
He says it was "very hard to take in initially", what had happened.
He said he stood in disbelief.
But he says "you have to remember that you're in charge".
"You have to switch off as a person and you have to remember that you're in charge and you have to deal with this", he adds.
"I wanted to run, but I had to do my job."
"A pervading smell that was coming up over the street... a smell of death."
He describes how the people he saw had "taken on an unusual colouring" from being covered in ash.
He says that upon arriving at the scene there were shop burglar alarms going off and a "horrendous amount of screaming".
He also noted the "smell coming up over the street".
He says the situation "got worse and worse" as he made his way down Market Street.
He recalls hearing the explosion.
"I was crouched down and looked behind me and saw the plume of smoke."
He says he "couldn't believe" where the bomb had exploded.
He says it was immediately clear that the bomb had gone off in the direction that people had been moved.
After the clearance operation following the bomb warning, Mr Marshall recalls around five cars on either side of the road outside the court house.
He says he believed that one of those cars had the bomb inside.
"And that's where I was standing."
He began to radio in the registration numbers of the cars near the court house.
"It was our understanding that the bomb was at the courthouse," he adds.
He says he became aware of two further warnings.
He also confirms that people continued to be moved down Market Street
A "godsend" for Mr Marshall was that a "large number of police officers who were due to go to Kilkeel" were rerouted to Omagh.
They were due to tend to an organised march.
He says that people were reluctant to clear pubs and bookmakers due to an attitude that it was just a bomb scare.
He says while most people listened to the warning but others were more awkward.
He says people in the bookmakers wanted to watch the end of the race and people in pubs wanted to finish their drinks.
He says he told these people "in no uncertain terms" to get out.
In his statement, Mr Marshall makes the point that within the warning there was no indication of the make model, colour or registration number of the car which contained the bomb or what shop it was parked beside.
"If we had of got any of that we wouldn't be sitting here today," he adds.
Mr Marshall says he travelled into the town with Constable Haslett.
He was informed by staff at Omagh Police Station that they had received a warning that a bomb had been placed in Omagh near the court house.
On hearing the familiar code word that was used, he "immediately" deployed cars to clear the area.
"The focus of our attention" was around the court house.
Mr Marshall says he told officers where to position to allow a parade to pass through the centre of Omagh.
He says he understood that he would also deploy traffic wardens.
He says he looks back on this with regret as it proved "costly" for them to positioned at the bottom of the town.
Mr Marshall says: "It was a normal day."
He briefed the section first thing and allocated tasks.
"It was a beautiful day," he said and the town was looking forward to a parade.
On the day of the bombing, Mr Marshall was duty sergeant at Omagh police station.
He says this entailed being in charge of the security of the station, the communications room and all of the patrol cars.
He says it was a uniform job.
Philip Marshall is a retired police officer who served for 30 years mainly in Tyrone.
He was the duty sergeant at Omagh station on the day of the bomb.
The inquiry has risen for a break.
In his final comments, he says "for the sake of the families of the deceased, I want to assure them that on that day their loved ones were treated with all the dignity and respect that myself and my colleagues could muster."
"We treated the dead as if they were our own," he adds.