WATCH: Tulsa Police Confirms Shooter Had Been Treated at Hospital, Targeted Doctor He Blamed for Post-Surgery Pain

A Muskogee law enforcement official confirmed the identity of the gunman who killed 4 people before committing suicide at a medical complex in Tulsa, Oklahoma on Wednesday.

The Daily Beast reports that the shooter was named as 45 year old Michelet “Michael” Louis. The outlet reported that they spoke with Louis’ niece, who said Tulsa Police called her family to tell him he was the perpetrator. Tulsa Police Chief Wendell Franklin held a press conference on Thursday, confirming the report and naming Louis as the shooter.

“We are so distraught,” she said. “I don’t even want to be associated [with the news] because I’m so disgusted.”

During his press conference, Franklin explained that Louis was a patient at St. Francis Hospital who had back surgery there last month. Following the surgery, Louis repeatedly called the hospital complaining of pain and asking for more treatment.

Franklin said that a day after Louis spoke with Dr. Preston Phillips, who performed the surgery, Louis bought a semiautomatic “AR-15 style rifle” from a local gun store. He previously bought a handgun from a local pawn shop 3 days prior.

As Franklin described the timeline of the shooting and the police response, he announced that authorities found a letter on Louis’ body. Franklin said the note “made it clear that [Louis] 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.”

Phillips and Dr. Stephanie Husen were both killed in the attack.

Multiple outlets report that the Muskogee Police Department investigated the shooter’s house after the attack to search for a possible bomb. No explosive device has been found, but the house is still under investigation in connection to the hospital incident.

Watch above, via CNN.