Hundreds of bullet casings, more than a hundred interviews with police officers and witnesses, hours of videos and multiple locations were all part of the largest crime scene in the history of the Dallas police Department.

“Because the shooting moved from location to location, it was important to protect a very large area of that crime scene,” said Assistant Chief Randy Blankenbaker.

It took 10 days to process the massive scene.

Federal agents and detectives meticulously logged every piece of evidence. "They have literally taken hours worth of statements from witnesses and people who were involved in the incident," said Chief Blankenbaker.

The Dallas Police Department's Special Investigate Unit has worked almost an entire year with the FBI, piecing together a timeline that starts from the moment the first shot was fired until the Dallas Police Department sent in a robot with C4 explosives to blow up the shooter.

Detectives have gone over frame by frame of videos that showed the moment their brothers in blue were killed.

“This stretches really the limits of what we should be asking them to do and what they have to do because of the emotional boundaries it approaches,” said Chief Blankenbaker.

Everything had to be processed, including the bodies of the officers killed.

Officer Brent Thompson's family told WFAA that they weren't allowed to touch their son in the hospital room.

"I wanted to touch him, and they said you can't touch him because he is part of a investigation,” said Sam Thompson.

Because so many officers fired their weapons that night and used lethal force to stop the shooter, the case now goes to a Dallas County Grand Jury to review.

"The only fair, just, impartial thing to do would be to conduct this investigation with as mush diligence and meticulous way as we would any other investigation, where an officer used lethal force,” said Chief Blakenbaker.

Commanders on the scene say killing the shooter was the only way to keep him from killing others. A grand jury will decide if it was necessary.