During the training, law enforcement officers were “looking for people that may have been acting suspiciously. But we don’t know really what drew him to Mr. Brown. And, of course, we don’t know the words of the conversation (between Dermyer and Brown).”

While law enforcement officers at the bus station Thursday were doing a training exercise, Flaherty said, “it had an operational component. If that training led to some violation of the law, then they would deal with it appropriately.”

Brown, traveling from the Raleigh-Durham area to Chicago, was carrying two bags. One contained two partially loaded 30-round clips and two boxes of ammunition, Flaherty said. The gun was legally purchased 13 months ago by another person, but authorities have not yet been able to determine how it got to Brown, he said.

“It’s very troubling he would have a gun,” Flaherty said. “It’s troubling that he was out, having the history he had, and able to travel on the bus line.”

Brown, Flaherty said, had an extensive criminal history in Illinois and was well-known to Aurora police. He described Brown as having a history of drug charges and a variety of violent offenses, including some involving guns.