CHICAGO (CBS) — Floyd E. Brown is a name well-known to central Illinois law enforcement. On Thursday, he added many more pages to his extensive rap sheet.

Breakfast time, shortly after 9 a.m.: It was supposed to be another day executing warrants for a U.S. Marshals Task Force. During that operation, Brown fired at the officers and killed Jacob Keltner, who was assigned to the unit from the McHenry County Sheriff’s Office. Brown then fled, to downstate Lincoln, Ill., near Bloomington.

Sources tell CBS 2 Investigator Brad Edwards that Floyd’s weapon was a high-powered rifle that could fire bullets at 3,000 feet per seconds, capable of rendering body armor useless. With Brown’s extensive criminal history, there was no way he could legally possess such a weapon.

The unit executed the court-ordered warrants on Brown for parole violations at the Extended Stay America hotel in Rockford. Those warrants stemmed from a December, 2018 burglary spree in Bloomington, during which he crashed into three cars fleeing the scene, sources said.

That alleged crime violated his probation for 2011 burglary convictions in McClean and Macon counties. He was sentenced to 13 years for those crimes—and served seven.

During the trial for the 2011 cases, he was purportedly recorded on the jailhouse phone saying: “When I get out of jail, I’m gone.” And, using a pejorative about police, ‘The [bleeps] better hope and pray I don’t get out.”

His criminal history dates back to 1997. He’s had four orders of protection filed against him. He has three domestic battery convictions, and a jail stint in 2001 for reckless discharge of a firearm.

In 2000, the first time he harmed a police officer, he served 75 days for aggravated battery of a peace officer.

The next big question for law enforcement officials: How did he get the long-gun used in today’s shooting?