INTERNATIONAL: Four people were killed, including a gunman, and multiple others were wounded in a shooting on Wednesday on a hospital campus in Tulsa, Oklahoma, police said.

A man armed with a rifle and a handgun killed four people inside a medical building in Tulsa, Oklahoma on Wednesday (June 1) before he was fatally shot, police said, in the latest of a series of mass shootings to rattle the United States.

Police arrived at the St. Francis Hospital campus three minutes after receiving a call about the shooting on Wednesday afternoon and followed the sound of gunfire up to the building's second floor, officials told reporters.

The officers made contact with the victims and the suspect five minutes later, officials said.

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Wednesday's incident in Tulsa came on the heels of mass shootings that have reignited debates about gun control. Two weeks before the Uvalde shooting, a white gunman killed 10 people at a supermarket in a Black neighborhood in Buffalo, New York.

Police in Tulsa said they were trying to determine the suspect's identity, who they estimated was aged between 35 and 40, and had no details yet on his motive.

The building contains doctors' offices including an orthopedic center.

The White House said President Joe Biden had been briefed on the shooting and offered support to state and local officials in Tulsa, a city of some 411,000 people that sits around 100 miles (160 km) northeast of the capital Oklahoma City.

Officers were still working to clear the St. Francis Hospital campus, the Tulsa Police Department said on Twitter.

Captain Richard Meulenberg told ABC that police received a call about a man with a rifle on the second floor of a building on the medical campus and that "it turned into an active shooter situation".

By the time officers arrived on the scene, "they found a few people have been shot. A couple were dead at that point," Meulenberg said.

"We also found who we believed to be the shooter and still believe to be the shooter, because he had a long rifle and a pistol with him," Meulenberg added.

It was not immediately clear how the suspected gunman died.