WASHINGTON

Police were searching Wednesday for a prisoner who overpowered a guard, took his weapon and escaped from a hospital in a Maryland suburb of Washington, a state police spokesman said.

About 8 a.m., a prisoner who was at Laurel Regional Hospital for treatment took the weapon of a prison officer and fired it in an apparent attempt to free himself from his shackles, Maryland State Police spokesman Sgt. Arthur Betts told CNN.

Police identified the escaped prisoner as Kelvin Polk, 45, who was serving life plus 40 years at the Jessup Correctional Institution for kidnapping, carjacking and robbery.

Polk was admitted to the hospital about 2 a.m. Monday for chest pains. He was described as a black male, 6 feet 3 inches tall and weighting about 235 pounds, CNN affiliate WBAL reported.

There were no reports that anyone at the hospital had been hurt, Betts said.

But CNN affiliate WJLA, citing police, reported the man then carjacked a blue Toyota Camry driven by a relative of a hospital employee and shot the driver, who was treated at the hospital for a minor injury. The Camry's Maryland license plate is MVC 433, WJLA reported.

The hospital was placed on lockdown until authorities determined that Polk was not in the facility, Betts said.

"They believe he is off the hospital grounds," he said.

The hospital is near residential areas, and three schools were on lockdown, according to a public information officer for the Prince George's County Schools System.

Maryland State Police provided a phone number -- 301-345-3101 -- for people to call with information about Polk.