Representatives of the department will be meeting as soon as Thursday with Brown's mother. Ferguson police are working with the Department of Justice and the NAACP to arrange that, Jackson said. He did not elaborate.

Some have complained about how long Brown's body was in the street. Jackson said Brown's body was left on the street to make sure the investigation wasn't compromised. He did not say exactly how long it was before Brown's body was removed.

"You only get one chance at that crime scene," Jackson said. "We wanted to make sure we got it right."

He said shots were fired from a nearby building several times while investigators were working, slowing the investigation.

"Now we have to make sure the crime scene investigators are safe," he said.

He said Brown's body was covered when possible. That's been another point of dispute on social media and among protesters.

Jackson said the officer who shot Brown suffered facial injuries and was taken to a hospital. He didn't address how the injuries occurred. He said he's aware of no video of the encounter between the unnamed officer and Brown.