A gunman opened fire at a Birmingham, Alabama, hospital, wounding two men before turning the gun on himself Wednesday night, police said.

Birmingham police Lt. Peter Williston said police were called at 6:55 p.m. Police found two victims along with gunman who died of self-inflicted gunshot, Williston said.

Capt. H.R. Watson of Birmingham Fire and Rescue told news reporters that one victim was in critical condition with multiple wounds.

He said authorities are unsure of the shooter's relation to the victims and whether the victims worked at the hospital. He added that police "still have a lot to find out."

Police say the scene is secure and authorities issued an "all clear" alert about 7:45 p.m. after ordering students to shelter-in-place.

Al.com reports paramedics were entering the building through the same-day surgery entrance and being taken to the second floor where the victims were believed to be located.

UAB tweeted late Wednesday that all surgeries scheduled for Thursday at the hospital where the shooting occurred were being canceled.

UAB Highlands is a campus of UAB Hospital, which is part of the medical school at the University of Alabama at Birmingham.