PITTSBURGH — Investigators have tracked down the parents of a gunman who killed one and wounded six others before he was fatally shot by police at a Pittsburgh mental hospital last week, a medical examiner said today.

Dr. Karl Williams, Allegheny County’s medical examiner, said John Shick’s parents were notified by the U.S. Coast Guard on Sunday morning that he had been killed. The Associated Press has not been able to reach Laurence and Susan Shick, who were reportedly sailing near the Bahamas when the shooting spree occurred, which is why Pittsburgh-area authorities enlisted the Coast Guard in finding them.

Authorities were still trying to determine why Shick opened fire Thursday in the lobby of the Western Psychiatric Institute and Clinic.

Investigators were studying handwritten notes, medication and other items recovered from the 30-year-old gunman’s apartment on Friday, the day police positively identified him.