Tributes have been paid to the five police officers killed in last night's attack
Recordings have emerged of policemen making desperate pleas for back-up after a shooter began targeting officers who were patrolling a protest in Dallas.
The audio, broadcast by CNN, appears to be from the beginning of the stand-off, which killed five officers and wounded another seven.
A police dispatcher is heard calmly informing colleagues in the field: "Shots fired, officer down."
Officers at the scene respond by saying the suspect is armed with a long rifle, with one cop breathlessly saying: "We don't know where the hell he's at."
Another shouts: "Slow down, he's in the damn building right there."
The police scanner recording emerged as details surfaced about the officers who were killed in the attack.
Meanwhile, details have begun to emerge about three of the slain officers. The names of the two other deceased have not yet been released.
A transport police officer in Dallas since 2009, the 43-year-old was killed two weeks after marrying a fellow officer.
Mr Thompson had served in Iraq for four years as a private contractor training local police forces.
Go Fund Me Account set up in honor of DART Police Ofc Brent Thompson to help his family during this tragic event https://t.co/U7oYJEG96t— dartmedia (@dartmedia) July 8, 2016
The 32-year-old was also a veteran and had served three tours in Iraq. In addition to his work as a Dallas policeman, he was in the military reserves.
Mr Zamarippa was married with a young daughter and a stepson, with his uncle saying: "He enjoyed the job - that was his calling."
His brother paid tribute to him in a post on Twitter.
The 40-year-old's death was confirmed by the Wayne County Sheriff's Office in Michigan, where he had worked as a deputy in the state's jails from 2003 to 2007.
His brother-in-law described him in an interview with the Washington Post as a "really caring" person with a "big heart".