A gunman who killed four people at a Tulsa hospital Wednesday targeted a doctor who had treated him and bought the AR-15-style rifle used in the shooting on the day of the attack, police said.
Officials said the gunman was armed with a rifle, which he had purchased at 2 p.m. Wednesday, and a handgun when he went to St. Francis Hospital shortly before 5 p.m.
He opened fire inside the Natalie Building, killing Dr. Preston Phillips and Dr. Stephanie Husen, receptionist Amanda Glenn and a patient, William Love, police said at a news conference Thursday.
Tulsa Police Chief Wendell Franklin said that the shooter was a patient of Phillips and underwent back surgery May 19.
The shooter was released May 24 and repeatedly complained of being in pain in the days afterward. On May 31, the shooter received additional treatment at the hospital but still complained of pain, Franklin said.
The chief said the shooter “blamed” Phillips for his pain.
Hours before the killings, the shooter purchased an AR-15-style rifle from a gun store. Days before that, he had bought a semi-automatic pistol from a pawnshop, according to Franklin.
The chief said the shooter had a letter with him “which made it clear that he came in with the intent to kill Dr. Phillips and anyone who got in his way.”
“He blamed Dr. Phillips for the ongoing pain following the surgery,” he said.
The shooting began around 4:52 p.m. on the second floor of the five-story building. A doctor was on a video call with someone and told the person to call 911 to report shots fired, the chief said. Police received the first report at 4:53 and were on the scene 3 minutes later.
Franklin said the shooter parked in the parking garage and entered through a second-floor door. As soon as he walked in, “he began firing at anyone that was in his way,” the chief said.
The shooter died from an apparent self-inflicted gunshot wound as officers were making their way to the second floor. Either before the chaos or during, the shooter called his wife who alerted authorities, according to Franklin.
Franklin said Phillips was found dead in an examination room. Other people were wounded but a hospital official did not say how many or if it was from gunshots. Those who were wounded have been treated and released, the hospital official said.
The shooting follows killings in Buffalo, New York; Uvalde, Texas; and New Orleans. A span of violence also hit several U.S cities over the Memorial Day weekend, leaving at least 156 people dead and 412 injured from 5 p.m. ET Friday to 5 a.m. Tuesday, according to a preliminary count by The Gun Violence Archive.
This is a developing story, please check back for updates.
Minyvonne Burke is a senior breaking news reporter for NBC News.
Tim Stelloh is a breaking news reporter for NBC News Digital.