Law enforcement officers block the entrance to the Louisiana State Police headquarters after 3 police officers were killed early this morning on July 17, 2016 in Baton Rouge, Louisiana. According to reports, one suspect has been killed by police. [Photo/VCG]

In Kansas City, police cordoned off streets within a block or more of the house where Long lived in a working-class neighborhood of mostly black residents.

Bob Phillips, 24, had lived across the street from Long for a month but said he did not know him. Phillips said he was surprised to hear that Long lived nearby.

"It's a quiet neighborhood, kids out playing," he said.

Missouri court records show Long divorced his wife in 2011, with no children at the time. There was no criminal record for him in Missouri.

Long was a defendant in a case involving delinquent city taxes. It was filed in March and was dismissed in June, according to court records.

Long attended the University of Alabama for one semester in spring 2012 and made the Dean's List, according to university spokeswoman Monica Watts.

"The university police had no interaction with him while he was a student," she said in an email.

Brady Vancel, a witness to the Baton Rouge shooting on Sunday, said on CNN that he ran into the suspect, who was dressed in black, a few minutes before the police officers were shot. The man was carrying an AR-15 assault rifle and wearing a ski mask, Vancel said.

The gunman "looked up and he saw me. We stopped, I froze, he froze for a second, and he turned around and ran in the opposite direction the same time I turned around and ran in the opposite direction," Vancel said.