Harrowing footage has emerged during the fallout of a sniper-shooting on police at a Dallas protest.
The video captured the moment a police officer took on one gunman from behind in an attempt to bring him down during the attack.
Instead, the gunman turns, rushes at the officer, and executes him in the back at point-blank range.
The officer’s bullet bounced from the gunman’s jacket, leaving him vulnerable to the gunman in a moment that proved fatal.
“He just turned around and shot him,” witness Ismael Dejesus told CNN News.
“The police officer was down and he shot him maybe another three or four times in the back,” he said.
Dejesus said he suspected the gunman was wearing body armour, armed with what “looked like an AR-15 assault rifle, and had so many magazines they were “falling out of his pockets.”
It is believed the gunman was one of many involved in a coordinated attack during a Black Lives Matter protest.
At least four people have been killed in the shooting so far, with 11 police officers and one female bystander wounded.
Dallas police suspect there may also be bombs planted across downtown Dallas.
There are currently three shooters in custody. A fourth is engaged in a standoff with police, the Guardian reports.
The Black Lives Matter protest followed the deaths of two black men, Alton Sterling in Lousiana and Philando Castile in Minnesota. Both were shot dead by police in incidents caught on video.
Today's shooting took place just before 9pm as the protesters were marching near Lamar and Main St, Nine News reports.
Video from a Fox News crew captured the sound of gunshots followed by screams from the crowds, who just moments earlier were chanting, “don't shoot”.