A patient gunned down his surgeon and three other people in a mass shooting at a Tulsa, Oklahoma, medical building on Wednesday after blaming the doctor for his pain.

According to ABC News, on May 19, the gunman had back surgery performed by Dr. Preston Phillips, one of the four people killed in the shooting.

A letter recovered on the suspect, Michael Louis, said

…he came 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.”

Louis bought an AR-style semi-automatic rifle just hours before the shooting. He also bought a 40-caliber pistol from a pawn shop on May 29.

The three others killed were Dr. Stephanie Husen, receptionist Amanda Green and patient William Love. Franklin said,

They stood in the way so the suspect gunned them down.”

Louis was released from the hospital on May 24, five days after his surgery and after his release, the suspect called several times over several days complaining of pain and wanting additional treatment.

On Tuesday, Phillips saw the suspect again for additional treatment and on Wednesday, the suspect called the doctor complaining of back pain and wanting additional help.

Police said 30 minutes after the shooting, authorities got a call from a woman who said that her husband killed multiple people at Dr. Phillips’ office. Louis contacted his wife before (or during) the shooting

to let her know what he had done.”

Hospital officials said that there’s no evidence that Phillips had any concerns about Louis.

The shooter died at the site from an apparent self-inflicted gunshot wound, police said.

BREAKING: Tulsa mass shooter allegedly gunned down his doctor, three others after asking for help with pain. https://t.co/ZMpc19QWh2

— ABC News (@ABC) June 2, 2022

(Photos, Tulsa Police Dept.; via ABC News)