The gunman in Tulsa who killed five people, including himself, has been identified as Michael Lewis, a former patient of Dr. Preston Phillips, who had performed back surgery on Lewis just 13 days before he was gunned down along with three other people.

Lewis had only been out of the hospital for seven days before deciding to purchase an AR-15 and kill Dr. Phillips, along with Dr. Stephanie Husen, 48, a sports medicine specialist. Amanda Green and William Love are named as the other two victims of Wednesday night’s shooting, but it is still unknown if they were hospital staff or patients.

Lewis’ motive was determined by a note that authorities found on his person, implying that he was intending to turn the gun on himself after killing Dr. Phillips.

Tulsa Police Chief Wendell Franklin confirmed that Lewis “came in with the intent to kill Dr. Phillips and anyone who came in his way,” Franklin said, according to Yahoo! News. Dr. Phillips was inside one of the buildings at the St. Francis Health System campus.

Unlike the Robb Elementary School shooting in Uvalde, Texas, which saw officers refusing to engage the suspect for over an hour, officers engaged Lewis immediately, but he took his own life before law enforcement was able to apprehend him.

“The gunshot was at 4:48 p.m. approximately 39 seconds after the first officers entered the building,” Franklin said.

Fox News reports, “Lewis expressed that he was in pain and was not getting relief,” Franklin said. “And that was the circumstance surrounding this entire incident.”

An Oklahoma City Bomb Squad was called in to sweep the building for any explosives that Lewis may have left in the building. “No devices were found,” Lynn Hamlin said, according to MSN.

Dr. David Holden, the Oklahoma State Medical Association President, had this to say: “Oklahoma’s hospitals, clinics and doctors’ offices are places for healing and should be safe for all. And while there will be much to discuss regarding this tragedy in the days and weeks to come, we stand with our fellow physicians and health professionals in mourning those who were killed and injured due to this devastating event.”

There have been nearly 300 mass shootings in the U.S. since the beginning of 2022.