Five people, including the shooter, were killed in a hospital campus shooting on Wednesday evening in Tulsa, the second largest city in the U.S. state Oklahoma, authorities said.

Tulsa Police Captain Richard Meulenberg said the shooter was reported "down" around 5:30 p.m. local time and the situation at the building, which was active about four to five minutes, was being treated as "a catastrophic scene."

"We know there are multiple injuries, and potentially multiple casualties," the police department said in a Facebook post.

The shooter was armed with a rifle and a handgun and fired both weapons at the Natalie Medical Building, a physicians' office building on the St. Francis Hospital campus, according to Tulsa Police Deputy Chief Eric Dalgleish.

Dalgleish said the shooter's fatal wound was self-inflicted.

Police have not identified victims or anyone specifically targeted by the gunman.

The Tulsa Police Department earlier in the day said they had responded to the shooting, and asked the public to stay away from the scene and "yield to all emergency vehicles."

There had been 214 mass shootings in the United States so far this year, including 27 school shootings and up to approximately 10 mass shootings every week, reported media organization The New Republic on Saturday, citing the Gun Violence Archive.

More than 17,000 people have died in gun-related episodes across the United States over the past five months, including approximately 653 children and teenagers.

"This is a uniquely American phenomenon, for no other reason than the fact that, unlike everywhere else in the world, there are too many readily available guns in America," said the report written by Jason Linkins, deputy editor of the magazine. 

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(With input from agencies）