A police vehicle arrives at Johns Hopkins Hospital, Thursday, Sept. 16, 2010. (AP/Alex Dominguez)
BALTIMORE (CBS/AP) Baltimore police say a lone gunman shot a doctor on the eighth floor of a Johns Hopkins Hospital building in Baltimore, was believed to have barricaded himself in a relative's hospital room.
There were conflicting reports about whether the shooting suspect was still at-large.
Parts of the Nelson Building, the main tower at Johns Hopkins, was put on lockdown around 11:15 a.m. Thursday, and other sections of the East Baltimore hospital campus were evacuated, after reports of shots being fired, according to The Baltimore Sun.
A nurse who worked on the floor where the injured doctor was shot told the paper that the gunman was unhappy about the way his mother was being treated and had threatened to jump out of a window when the shooting occurred.
"I started running," The nurse told the Sun. "When you hear gunshots you run."
Baltimore police said they were setting up a tactical operation to deal with a gunman who is holed up on the eighth floor.
The doctor was rushed to surgery and is expected to survive, police spokesman Anthony Guglielmi said. He said he did not know the relationship between the gunman and the doctor.
The hospital said in a statement that the doctor is a faculty physician but it could not release more information because of privacy policies.
A spokesman for Johns Hopkins hospital in Baltimore earlier said the gunman had been caught, but Guglielmi says that's not the case.
Guglielmi said some parts of the hospital were being evacuated, but not the entire massive complex in east Baltimore. He says he doesn't know the doctor's condition.
"The doctor will be OK," Guglielmi said. "He's in the best place in the world - at Johns Hopkins hospital."
A man shot a faculty physician as well as his own mother before killing himself at  in Baltimore, Maryland. The shooting occurred on the eighth floor of the Nelson Building, the hospital's main building. Baltimore police found the suspected shooter, who had been barricaded inside his mother's hospital room for several hours before killing himself and his mother.

At around 11:15 a.m.  (1515 ), an unnamed doctor was shot in the chest at a patient area of the Nelson Building's thoracic center. All major hospital facilities were placed under a lockdown, and some medical personnel were evacuated from the Nelson Building. The doctor was sent to surgery at the hospital, and police spokesperson Anthony Guglielmi said that the doctor will likely survive the incident. He was not aware of any connections between the suspect and the doctor, who was in critical condition.

A nurse at the hospital told '''' that the shooter was dissatisfied with how his mother had been treated and even said that he was going to jump out of a window. The nurse said that, upon hearing gunshots, she ran.

Earlier, Baltimore area police said that they were "in the process of a tactical operation" to capture the gunman, who was holed up on the eighth floor. A spokesperson for the  (FBI) said that it had been assisting local police in the incident. A Johns Hopkins spokesperson had previously said that authorities had taken the shooter into custody, but police said that the report was incorrect.

The suspect, who had not taken any hostages, was described as a black man in his thirties. After a standoff lasting for three hours, law enforcement officers moved into his mother's hospital room, and found both him and his mother dead from gunshot wounds to their heads. The suspect was first identified as 50-year-old Warren Davis, and his mother as Jean Davis. Police later said that "Warren Davis" was an alias and that his real name was not known.

Baltimore Police Commissioner Frederick Bealefeld, who said that the department is "treating this case as a murder-suicide," said that no officers reported hearing the shots that killed the two.  Police had previously said that the gunman had been shot and killed by police, but police later said that that report was incorrect.