At least three people have been shot and multiple others injured in a shooting at a medical building which police have described as “catastrophic”.

Tulsa police said multiple people were shot at a hospital campus on Wednesday and “some unfortunately were killed”.

In a Facebook post made by the police department just before 6pm, police said the gunman was dead. It was unclear how the gunman died.

“Officers are currently going through every room in the building checking for additional threats,” police said. “We know there are multiple injuries, and potentially multiple casualties.”

St Francis Health System locked down its campus on Wednesday afternoon because of the situation at the Natalie Medical Building.

The Natalie building houses an outpatient surgery centre and a breast health centre.

Aerial footage from a TV helicopter appeared to show first responders wheeling someone on a stretcher away from the hospital building.

Dozens of police cars could be seen outside the hospital complex, and authorities shut down traffic as the investigation went on.

A reunification centre for families to find their loved ones was set up at a nearby high school.

Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives were also at the scene, a spokesperson said.