PITTSBURGH—A district attorney's office in Pittsburgh says they will subpoena records from Columbia University regarding a former student who killed a nurse and wounded several others at a psychiatric clinic in March.

Mike Manko, a spokesman for the Allegheny County District Attorney's Office, says Thursday that authorities have learned that the gunman, John Shick, received mental health treatments in New York as early as 2005. Shick graduated from Columbia in 2004.

Shick, 30, was slain by police after the March 8 shootings at UPMC's Western Psychiatric Institute and Clinic in Pittsburgh, and investigators have been trying to determine his mindset and any previous warnings about his behavior.

Columbia spokesman Brian Connolly did not immediately respond to a message seeking comment.