Jason Schneider, 36, died at the Maryland Shock Trauma Center, The Baltimore Sun reported. His alleged killer was at the same hospital in critical condition.
The shooting occurred around 5:30 a.m., police said. Schneider and other officers were in the house in Catonsville doing a room-to-room search for the subject of a warrant when gunfire broke out.
Police said Schneider returned fire.
Gov. Martin O'Malley ordered flags at Maryland state buildings to be flown at half-staff.
Schneider had been a member of the Baltimore County tactical unit for four years after joining the police department 13 years ago.
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