A gunman who killed four people at a Tulsa hospital on 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, identified Thursday as Michael Lewis, was armed with a rifle and handgun when he went to St. Francis Hospital shortly before 5 p.m.
He opened fire inside the Natalie Building wounding several people. Four others, believed to be a combination of patients and employees, were killed.
Tulsa Police Chief Wendell Franklin said at a news conference Thursday that Lewis was released from the hospital in May after undergoing back surgery and repeatedly complained about pain in the days afterward.
The shooter “blamed” his doctor, Preston Phillips, for his pain, Franklin told reporters and went to the hospital to kill the doctor and anyone else who got in his way.
Phillips was one of the victims found dead.
On Wednesday, Tulsa Deputy Chief Eric Dalgleish said that part of the shooting appears to have occurred inside an orthopedic facility on the building’s second floor, where the victims and gunman were found.
The shooter died from a self-inflicted gunshot wound as officers were kicking in a stairwell door to gain access to the building.
The shooting follows killings in Buffalo, New York; Uvalde, Texas; and New Orleans. A span of violence also hit several U.S cities over 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 story first appeared on NBCNews.com.