An Arlington County man who for years had devoted his life to caring for his elderly mother apparently lost control Thursday morning when he learned news about her medical condition. He pulled a gun from his waistband and shot a Johns Hopkins Hospital doctor in the chest before barricading himself in his mother's eighth-floor hospital room.

After a two-hour standoff, Baltimore police found Paul "Warren" Pardus, 50, dead on the hospital room floor and his mother, Jean Davis, dead in her bed. Police think Pardus killed his mother before turning a semiautomatic handgun on himself, a case authorities are treating as a murder-suicide.

Baltimore Police Commissioner Frederick H. Bealefeld III said Thursday that Pardus was getting a briefing about his mother's health at 11:11 a.m. in the sprawling hospital's Nelson Building when he "became emotionally distraught and reacted and was overwhelmed by the news of his mother's condition."

Pardus then pulled a gun out of his waistband and shot the doctor once in the lower chest. The doctor collapsed just outside Room 873, where Davis was confined to a bed, and Pardus ran into the room with his gun raised. SWAT team members found Pardus and his mother dead about 1:30 p.m.

The wounded doctor underwent surgery at Johns Hopkins on Thursday and was expected to survive, police said.

The midday shooting shocked the Johns Hopkins community, home to one of the nation's premier hospitals, and caused police and hospital officials to shut down parts of the Nelson Building while warning the rest of the campus of a gunman on the property.

The Johns Hopkins medical system employs more than 30,000 people and has more than 1,000 beds and 1,700 full-time doctors.

Pardus -- who legally changed his name from Warren Leo Davis in 1989, according to court records -- had a concealed-weapons permit in Virginia. Pardus was an employee of Diamond Transportation, a subcontractor for MV Transportation, which provides drivers for the MetroAccess program. MetroAccess transports disabled people in the Washington area.

A spokeswoman for California-based MV said Thursday that Pardus has been on leave since June 20.

Several people who live near Pardus's home on South Kenmore Street, just off of Glebe Road, in Arlington said he had barely been in the neighborhood for the past six months because of his mother's hospitalization. They said Pardus essentially lived with his mother at Johns Hopkins and stopped by their home infrequently to get a bag of clothes or other belongings.

"He was a very nice man," said Teresa Green, a next-door neighbor who said she often saw Pardus caring for his mother, who lived with him full-time for at least the past five years. "He was the only one there for her. It was like a 24-hour job for him."

Green said Pardus largely kept to himself, but they would talk occasionally when he was cutting his grass or working on his car.