A Baltimore homicide detective is in critical condition after being shot in the head Wednesday by a man who approached him in west Baltimore at about 4:30 p.m.

The officer, who's been with the Baltimore Police Department for 18 years, was shot in the head after approaching a man who was engaged in "suspicious behavior," said Police Commissioner Kevin Davis in a press conference that evening.

"We are doing everything we can to keep [the officer] stabilized and to take care of the injury to his brain," said Dr. Thomas Scalea, chief of the University of Maryland Medical Center's Shock Trauma Center.

A $64,000 reward was issued for information leading to the arrest of the suspect. A manhunt is under way in Baltimore and the surrounding area. The suspect was described only as a black male in a black jacket with a white stripe, Fox Baltimore reports.

“People who walk our streets with guns in their hands are killers. I want to describe this person as cold and callous,” Davis said. "He's out there right now and he now knows that he shot a Baltimore police officer. He knows it. He's well aware of it.

"My best guess is that there is more than one other person who is aware that this callous coward with a gun in his hand who shot a cop in the head tonight," he added.

The shooting was the second of a law enforcement officer in West Baltimore this month. Sgt. Tony Anthony Mason Jr., 40, a District of Columbia police officer who lived in Baltimore, was shot to death in the 2800 block of Elgin Avenue on Nov. 4. He was off duty at the time, the Baltimore Sun reports.