(NewsNation) —Tulsa police are responding to an “active shooter” situation at Saint Francis Hospital where at least four people, including the shooter, were killed Wednesday, Tulsa Police wrote on Twitter.

“Earlier this afternoon, we responded to a call about a man armed with a rifle at the Natalie Building at St. Francis Hospital. This turned into an active shooter situation,” police wrote in a Facebook post. “At this point, we can confirm the shooter is dead.”

Officers are currently combing each floor of the building to check for “additional threats,” police wrote.

“We know there are multiple injuries, and potentially multiple casualties,” officials said.

Tulsa Police told KTUL the scene inside the hospital was “catastrophic.”

A family reunification site has been established at a local high school about 1.2 miles away from the medical center, police say.

Saint Francis Hospital is the largest hospital system in Tulsa, according to retired Tulsa police officer Sean Larkin.

This is a breaking news story. Please check back for updates.