Dallas police have completed their investigation of the July 2016 ambush that killed five officers. The case has been sent to the Dallas County District Attorney for final review by a grand jury.
Nine other officers and two civilians were also wounded that night, as the gunman opened fire on officers near Main and Lamar streets downtown at the end of a rally against recent police shootings of black men elsewhere in the United States.
Suspect Micah Johnson was eventually killed by explosives carried by a police robot following a standoff with officers.
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One focus of the investigation was to determine whether Johnson acted alone in planning the ambush. No one else has been charged.
Streets near the crime scene were closed for more than a week to gather evidence.
It took more than 14 months to complete the probe, and lawyers familiar with police use of force investigations said Thursday that this one is very complicated.
"There were multiple crime scenes in this particular case. The shooter moved around," attorney Pete Schulte said.
Schulte is a former prosecutor and police officer who represented some of the Dallas Area Rapid Transit officers involved in this investigation.
"We know that the suspect died as a result of the police activity that night, however, there were five police officers who also lost their lives. So each one of those homicides have to be investigated and the leads that kind of go with them have to be followed and that can take some time," Schulte said.
Soon after the incident, police said about 300 witnesses and 170 hours of police body camera video would be included in their investigation.
Heath Harris, former chief assistant Dallas County district attorney, has presented use of force cases to grand juries in the past.
"I don't think there's been any allegation of misconduct from day one," Harris said. "Even though this guy had shot, ambushed numerous officers, they still gave him a chance to give up."
Federal agencies also participated in the investigation that was coordinated by Dallas police.
"There were a lot of agencies that wanted to take part to make sure we do everything we can to learn from this tragedy so that it never happens again," Harris said.
Harris and Schulte said grand jury review is routine in Dallas County for use of force cases and that use of the robot to stop the suspect appears to be justified.
"I think in a way it does give the families some closure," Schulte said. "But it's also to make sure that everything was reviewed in this case and all the evidence was looked at, everything was turned over and this is the right result."
The attack on police brought a tremendous display of grief with messages from around the world in front of Dallas Police Headquarters last year.
"It's going to be a while before we can truly heal from this," Harris said. "The criminal justice community, it's a family."
A spokesperson for the Dallas County District Attorney confirmed Thursday that prosecutors are preparing the case for grand jury review.
No date has been set.
The officers killed in the shooting included Dallas police Sr. Cpl. Lorne Ahrens, Officer Michael Krol, Sgt. Michael Smith, Officer Patrick Zamarripa and Dallas Area Rapid Transit Officer Brent Thompson.