Dispatchers received a 911 call shortly before 5 p.m. local time about a man walking with a rifle at the Natalie Building, a physicians' office building on the Saint Francis Hospital campus. When police responded, they said it turned into an active shooter situation, according to Tulsa Police Capt. Richard Meulenberg.
When police entered the building, they found multiple people shot in one area on the second floor, including in an orthopedic office, authorities said. The victims could be a combination both of employees and visitors, authorities initially said.
"Officers immediately rushed to the second floor where the shooting was taking place, when they got there they found a few people had been shot, a couple were dead at that time," Meulenberg told ABC News. "We also found at that time who [we] believe and still believe to [be] the shooter because he had a long rifle and a pistol with him."
The Tulsa shooting comes amid a spate of shootings in the U.S., including the Uvalde shooting in Texas where 21 people -- including 19 children -- were killed, and a mass shooting at a Buffalo, New York, supermarket that saw 10 Black people shot dead.
One of the Tulsa victims died after leaving the scene trying to seek medical aid, according to Meulenberg. It is unclear at this time how many others were wounded in the shooting, though Meulenberg believed it to be under 10.
The shooter died from an apparent self-inflicted gunshot wound, according to Tulsa Police Deputy Chief Eric Dalgleish. Police were still working to confirm the identity of the suspected shooter, a man believed to be between the ages of 35 and 40, Dalgleish said during a briefing.
It appears both weapons were fired, according to Dalgleish. It is unclear if the suspect was targeting anyone specifically, he said.
Police said they went through the five-story medical complex room by room to secure the building.
"We are doing a meticulous floor-by-floor, room-by-room search," Meulenberg said. "It's calmed down. We're trying to connect people and we're hoping not to find any victims
Police said they are also investigating a possible bomb threat that may be connected to the suspected shooter.
Authorities evacuated a home in Muskogee, Oklahoma, about 50 miles southeast of Tulsa, after receiving a tip that the suspect "may have left a bomb at this residence," Muskogee Chief of Police Johnny Teehee said Wednesday night.
A bomb squad was on scene and police were working to obtain a warrant to search the residence, he said.
Muskogee Mayor Marlon Coleman later said the bomb squad cleared the location of a potential threat, and that the scene had been "turned over to the necessary authorities."
The Tulsa Police Department said to stay away from the area of the shooting and that reunification for families will be at Memorial High School on the west side of LaFortune Park