The gunman who killed four people in a shooting at a Tulsa hospital appears to have ties to New Jersey.

NJ Advance Media reports that gunman Michael Louis lived in Newark before moving to Oklahoma in 2013. Relatives still live in the Garden State, according to the newspaper.

Authorities say that Louis may have called his family prior to Wednesday’s attack.

Louis purchased an AR-15 at a pawn shop just days before the shooting. He also had a handgun on him during the attack.

News 12 has also learned that it was a patient of Tulsa's Saint Francis Hospital who called 911 to report the shooting. That patient was in a video conference with the doctors who were killed. The doctors told the patient on the call that there was a gunman in the building.

Two doctors and two other people were killed in the attack.

Authorities say that Louis was previously a patient at the hospital and blamed one of the doctors for causing him pain from recent back surgery.