DEVELOPING: Dallas Police were in a standoff early Friday with a suspected sniper who, along with at least one other shooter, targeted law enforcement officers during a protest march, killing four and injuring seven other officers as well as one civilian. More suspects may be at large.

Dallas Police Chief David Brown said the suspect holed up in a downtown parking garage had exchanged gunfire with officers for 45 minutes and claimed "the end is coming", as well as saying that he had planted bombs across Dallas and wanted to hurt more officers.

Brown also said authorities had earlier taken a woman into custody near the garage. Two men were also being questioned after police pursued their vehicle away from downtown onto Interstate 35. 

 

Brown said "our assumption" is that the four suspects were "working together with rifles, triangulating at different positions." He had no information on a possible motive or the identities of any of the suspects. He also noted that police were not completely certain that every suspect was in custody.

Late Thursday, Brown confirmed the four fatalities — three Dallas PD officers and one transit officer — and said seven other officers and one civilian were wounded in the shooting. Three of the injured officers reportedly were in critical condition and two others were in surgery.

Brown said multiple shooters positioned themselves in two parking garages in downtown Dallas and "planned to injure and kill as many law enforcement officers as they could."

A Dallas police source estimated to Fox News that at least 60 rounds were fired over a "large kill zone." The source added that the shooting would have required considerable planning.

"It's a heartbreaking moment for the city of Dallas," Mayor Mike Rawlings said. "I ask everybody focus on one thing right now, and that is Dallas police officers, their families, those that are deceased [and] those that are in the hospital fighting for their lives."

Fox4 cameras captured protesters running away from the scene of the shooting shortly before 9 p.m. local time. A cameraman approached the scene and captured officers apparently lying on the ground.

Aerial images showed officers appearing to focus their search on a nearby parking garage, which may have served as the snipers’ perch.

Witness Carlos Harris told the Dallas Moing News the gunfire was "strategic. It was tap-tap-pause. Tap-tap-pause."

Texas Gov. Greg Abbott released a statement saying he has directed the Texas Department of Public Safety director to offer "whatever assistance the City of Dallas needs at this time."

"In times like this we must remember -- and emphasize -- the importance of uniting as Americans," Abbott said.

The protesters had gathered after a Minnesota officer on Wednesday fatally shot Philando Castile while he was in a car with a woman and a child in a St. Paul suburb. The aftermath of the shooting was purportedly livestreamed in a widely shared Facebook video.

A day earlier, Alton Sterling was shot in Louisiana after being pinned to the pavement by two white officers. That, too, was captured on a cellphone video.

Michael Bautista told KDFW the protest march had been "very peaceful" before the shooting started.

Brittany Peete, a demonstrator, told the Associated Press she didn't hear the gunshots, but she "saw people rushing back toward me saying there was an active shooter."

Peete said she saw a woman trip and nearly get trampled as people ran to get to safety.

"Everyone just started running," Devante Odom, 21, told The Dallas Moing News. "We lost touch with two of our friends just trying to get out of there."

Fox News' Bret Baier and the Associated Press contributed to this report.