UPDATE: According to authorities, five officers are dead and an additional seven injured during the shooting in Dallas on Thursday night. Cops reportedly have three of the four suspects in custody, while a standoff continues to bring the last one in. The suspects are not talking, Chief David O. Brown of the Dallas police says: “We just are not getting the cooperation we’d like, to know that answer of why, the motivation, who they are.” 
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Four Dallas police officers were killed and seven others were wounded Thursday night during a demonstration protesting the police shootings in Minnesota and Louisiana this week, according to Chief David O. Brown of the Dallas police.
One of the gunman is “cornered,” the Dallas Police Department said in a press conference. The Dallas police chief said that the officers were attacked by two snipers, neither of whom have been apprehended. Some of the officers were shot in the back. “We believe that these suspects were positioning themselves to in a way to triangulate themselves from two different perches,” Brown said.
The police are appealing for help in apprehending the shooters.
“Our worst nightmare happened,” Dallas Mayor Mike Rawlings said. “It is a heartbreaking moment for this city.”

The gunman fired from “elevated positions during the protest,” according to the Dallas Police Department.

The police department has released a photo of a “person of interest” in the shooting, identified as Mark Hughes. His brother Cory Hughes, one of the organizers of the protest, said Mark isn’t the gunman and handed his weapon over to police after the shooting.

Mark Hughes turned himself in, the department tweeted, and while police initially calledhim a suspect, he is now a person of interest. Another alleged suspect is in custody and a suspicious package was discovered near that suspect's location. The package is reportedly being secured by a bomb squad.
This story is developing...