BOULDER, Colo. -- A man in a wheelchair who threatened to blow up Boulder Community Hospital with a detonation device strapped to his oxygen tank has been shot once in the chest, ending a four-hour-long standoff, police said.

The man, identified as Terrance Baughman, 32, is being treated for a life-threatening gunshot wound to the chest. He was whisked away on a gurney to the emergency room, Denver station 7NEWS reported.

It's not known if he was in front of the hospital or just inside it when he was wounded, but reporters at the scene said they heard a loud bang coming from the hospital entrance at about 1 p.m.

A police spokeswoman said a bomb technician was assessing the device that was attached to his wheelchair to determine whether or not it is a threat.

The bomb squad will be using a remote-controlled robot to remove the device and bring it down Balsam Avenue to North Boulder Park, where the device will be detonated, said police spokeswoman Sarah Huntley.

Huntley said agents "are still in the midst of the operation" and the area is still not secure.

Baughman, who was once a patient at the hospital, was not wheelchair-bound but was using the wheelchair as part of his threat, Huntley said.

Streets around the hospital are cordoned off, and traffic in the area has been diverted.

The front part of hospital has been partially evacuated and officers were discussing if more of the building should be cleared, including some patients.

"There are no patients or visitors who are in any danger," hospital spokesman Rich Sheehan told the Boulder Daily Camera. "The police have estimated a safety zone for us... based on the size of the package the gentleman was carrying, and we have evacuated all patients, staff and visitors beyond that safety zone."

Baughman was just outside the emergency room when the alert went out shortly before 9 a.m. Police negotiators had been talking with him, but it's not known whether Baughman communicated any demands.

Police asked that anyone who may know Baughman contact the Boulder Police Department.

Huntley said ambulances are being diverted to other hospitals nearby, since the streets around Boulder Community Hospital have been cordoned off and the hospital remains on lockdown.

People who have doctor's appointments at Boulder Community Hospital are being asked not to go to the hospital today.

The FBI, the Bureau of Alcohol Tobacco Firearms and Explosives and Boulder County SWAT teams are assisting Boulder police at the scene.