At one point a gunman emerged from the crowd and fired at least one shot at police.
It can be seen around 1 minute 55 seconds into the footage.
Dissident republicans were blamed for the violence and a senior police officer said those responsible were "no better" than Islamic State terror group Daesh.
Video footage from the hours of trouble on Sunday night has emerged which appears to show the gunman firing.
Police in the Co Armagh town remain on high alert after coming under sustained attack from rioters, some reportedly as young as eight years old, while attempting to make safe a potential bomb on the railway line.
It came as police probed the second bomb alert in 24 hours - after examination the two suspicious objects were later declared as hoaxes.
Twenty five paint bombs, bricks and other masonry were thrown by a large and aggressive crowd who gathered at around 9pm and remained until the early hours of the morning.
No police officers or members of the public were injured however a number of police vehicles were damaged.
Helicopter air support, specially trained riot police from other parts of Northern Ireland and dog teams had to be brought to deal with the trouble.
Speaking at a press conference Superintendent David Moore said: "The people that are behind this have no ideology, they have nothing to offer, in many respects they can be compared to Daesh, they have got little to offer but destruction in their own communities."
Daesh is a name for the terror group also known as Islamic State which is fighting for territory in Iraq and Syria.
"We are very lucky not only to be dealing with the loss of life or serious injury to a police officer but we could be dealing with any member of the community in the same position this morning."
Mr Moore added: "The work of dissident republicans is evident here, not in any way organised, because it is the easiest thing to drop something on a railway line and have someone drunk batter on the window of a crossing guard's booth.
"It is the easiest thing to make phone calls...to try their best to confuse the police response.
"Eventually we deployed in a very careful, tactically sound way and what did we find? Five hours of sustained violence waiting for us."
The violence and disruption caused by the alerts were met with widespread condemnation.