PITTSBURGH — The mother of a mentally ill gunman who killed one employee and wounded five other people at a Pittsburgh psychiatric hospital is the target of a pending lawsuit to be filed by the slain worker's estate.

The document filed Thursday is a writ of summons, which doesn't set forth legal claims, but gives notice that a lawsuit will be filed by the estate of Michael Schaab, who was killed in the March 8, 2012 shootings at the Western Psychiatric Institute and Clinic.

Thirty-year-old John Shick was killed by University of Pittsburgh police who responded to his rampage, and his mother, Susan, of Green Cove Springs, Fla., is listed as the only defendant.

Susan Shick is also being sued by a receptionist who was critically wounded. Her attorneys didn't immediately return calls.