Detainees were being loaded out of a van when the gunfire erupted, according to a senior ICE official. Some detainees were still in the van when the shots rang out, and ICE agents ran back into the gunfire to bring the rest of them to safety in a move that "likely saved more lives," the official said.

The sniper who opened fire on an Immigration and Customs Enforcement field office in Dallas left behind notes saying he acted alone in an attack intended to kill and "terrorize" ICE agents, whose work he viewed as "human trafficking,

New surveillance video from the Dallas ICE facility reveals moments from the shooting as ICE agents and detainees tried to escape from the vans under fire on Wednesday morning as sniper targeted the facility​.

Video exclusively obtained by ABC News shows the moment gunfire erupted outside the Dallas Immigration and Customs Enforcement field office on Wednesday, killing one detainee and critically injuring two others.

A shooter opened fire at an ICE facility in Dallas on Wednesday, killing one detainee and critically injuring two others.

Authorities identified 29-year-old Joshua Jahn, who died from a self-inflicted gunshot wound, as the sniper who killed one detainee and injured two others Wednesday.

One of the people who suffered serious injuries is a Mexican national, according to the Mexican Ministry of Foreign Affairs.

A shooting Wednesday outside an ICE facility in Dallas killed one detainee and critically injured two, officials said. The shooter, identified as Joshua Jahn, is also dead.

The gunman who attacked a Dallas ICE facility sought "real terror" for agents and "searched apps that tracked the presence" of ICE personnel, the FBI says.