Dallas police say multiple pieces of evidence were seized from the Mesquite home of shooting suspect Micah Xavier Johnson, an Army veteran they say shot 14 people, killing five police officers, Thursday night.
Five police officers were shot and killed and seven more injured when Johnson, in an elevated position, opened fire in the city's downtown area. This compares with 18 at this point in time in 2015, said Nick Breul, director of research for the fund in Washington, D.C.
He was killed by a robot-delivered bomb after the shootings, which marked the deadliest day for US law enforcement since the September 11, 2001, terrorist attacks.
"That's certainly a concern for us".
Johnson died later after a standoff with police. "It's really an assassination".
Two law enforcement sources told ABC News that police have found no connection between Johnson and the three people detained during the overnight shootings. All four were killed.
The group was created in Dallas previous year to oppose police brutality, teaches self-defence and conducts patrols in areas where black men have been killed by the police. Omar Cannon, 44, Misty McBride, 32, and Jesus Retana, 39, are three other mass-transit officers who were injured during the attack.
"'I don't know what happened, but by the Bank of America building, there was a shooting; I ran, I dropped my phone'".
The Black Lives Matter rally was one of a number held across the United States in response to two fatal police shootings of black men, in Minnesota and Louisiana, this week.
Intent on killing white people, particularly cops, according to the Dallas police chief - himself an African American.
Cochran's shock mirrored the apparent frustration expressed by authorities who said that a review of the gunman's background left no immediate signal that might betray his mission - as expressed to police negotiators shortly before his death - to "kill white people, especially white officers".
Dallas Police Chief David Brown blamed "snipers", but it was unclear how many shooters were involved in Thursday's attack.
FBI investigators look over the crime scene in Dallas, Texas on July 8 following a Thursday night shooting incident that killed five police officers. Johnson said he didn't belong to any movement, including Black Lives Matters, and that he acted alone, a contention police continue to investigate.
The Dallas shooting occurred in the middle of a peaceful demonstration Thursday on the streets of downtown Dallas.
Both incidents were captured on video, reigniting what has become a national debate.
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".
"You can't shoot second if you're a person and you're dealing with somebody's who is armed", Bielat said.
"They can't take them to the park because they're not sure who's going to be shooting", Sherie Williams said.
Northrop Grumman Remotec, which calls itself the largest providers of robots to first responders, declined to comment and referred all questions to the Dallas police department.
"We could say the same things about white hate groups that inspire xenophobia or hatred against Muslims", said Woods, of Houston.