Tulsa, Oklahoma - Four people were killed and multiple others were wounded during a mass shooting Wednesday at a medical building in Tulsa, Oklahoma, police said.

The shooter died by suicide, Tulsa police Officer Eric Dalgleish told reporters outside the St. Francis Hospital.

Officials did not say how many people were wounded.

The shooter came in at 4:52 PM and police were on the scene four minutes later, Dalgleish said. Officers engaged the shooter at 5:01 PM and he shot himself shortly afterward.

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Police officers locked down the building and went floor by floor to evacuate people and confirm there was only one attacker. Dalgleish said the shooter, described only as a Black man in his late 30s,was carrying a rifle and a pistol.

Police did not immediately reveal anything about a possible motive for the shooting.

"This campus is sacred ground for our community." Tulsa Mayor G.T. Bynum said. "This has been the facility, more than any other, that has worked to save the lives of people in this city."

Tulsa resident Kalen Davis told CNN he was waiting in traffic at about 5 PM local time when he saw multiple police cars speeding toward the hospital site.

"I just knew that it was a shooting situation because I saw police running with rifles," Davis told CNN. "That's when I got emotional."

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Debra Proctor, a nurse, told CNN of the "shocking" scene she witnesses while waiting for a doctor's appointment in another building at the hospital complex.

"Police were everywhere in the parking lot, up and down the surrounding blocks," Proctor said. "They were still arriving when I was leaving."

The shooting comes just eight days after an 18-year-old gunman murdered 19 children and two teachers at an elementary school in Uvalde, Texas.

Ten days before that, another 18-year-old targeted a Black grocery store in Buffalo, New York. The white supremacist killed 10 Black people at the massacre at a Tops supermarket before police detained him.

"President [Joe] Biden has been briefed on the shooting in Tulsa, Oklahoma," press secretary Karine Jean-Pierre tweeted.

"The White House is closely monitoring the situation and has reached out to state and local officials to offer support."

According to the Gun Violence Archive, which tracks incidents of gun violence and crime in the US, this was the nation's 223rd mass shooting this year, where a mass shooting is defined as four or more victims killed or injured.