The gunfire started Thursday night as demonstrators marched against the shooting deaths of two African-American men by police in Louisiana and Minnesota.
A total of 11 officers were shot, and some of the six officers injured are undergoing surgery, authorities said.
It was the deadliest single attack on law enforcement since the 2001 terror attacks, when 72 officers died, according to the National Law Enforcement Officers Memorial Fund.
A total of 10 police officers were shot by snipers during the protests, Dallas Police Chief David Brown said. An 11th officer was shot during an exchange of gunfire with a suspect, authorities said.
Brown said it’s unclear how many suspects were involved, but three people are in custody.