CHICAGO (CBS) — Chicago Police Cmdr. Paul Bauer was fatally shot downtown on Tuesday after he confronted an armed offender. Here are five things we know:

1) Cmdr. Bauer heard on his police radio that tactical officers were pursuing a suspect who was running from the Renaissance Hotel near State/Lake. Bauer confronted the suspect at the Thompson Center, where Bauer was shot four times in the head, after a struggle on a stairway. Officers had attempted to question the suspect because he was acting suspiciously, according to police scanner reports.

2) The suspect has a long criminal record, including prison time for armed robbery and multiple arrests for drug possession. He was wearing protective body armor and was armed with a semiautomatic handgun, with a clip that held 30 rounds of ammunition, sources tell CBS 2.

3) The suspect was also in possession of 15 grams of heroin and bags of crack cocaine and marijuana, sources said. Police expect to charge him within 36 hours. CBS 2 is not naming the suspect because he has not yet been charged.

4) Bauer, 53, was named commander of the 18th District in 2016. He was a 31-year veteran of the department and once led the CPD’s mounted police force.

5) Bauer is survived by his wife and middle-school aged daughter. Mayor Emanuel called his death a ‘gut punch’ to the city.