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An unarmed, off-duty Skokie police officer was shot and critically wounded by a man who then apparently turned the gun on himself Thursday night at Niles West High School, Skokie police said.

Officer Donald Hennessy, 57, was working as a security monitor at the school, 5701 Oakton St., when he reported that he had been shot as an evening event was winding down at 10 p.m., Skokie police said.

When officers responding to the call encountered a man leaving the school property, the man put a gun to his head and fired one round, seriously wounding himself, police said in a statement signed by Skokie Police Chief William D. Miller.

Hennessy and the man who shot himself were both taken to St. Francis Hospital in Evanston around 10:15 p.m. Hennessy was in critical condition early Friday, according to hospital spokeswoman Alexia Patramanis.

The other man was pronounced dead at 10:48 p.m. Thursday, according to Patramanis. She said he was 27, however his identity was not released.

A preliminary investigation has determined the shooting was not related to the school, its students or faculty, Miller said.

Besides Skokie police, Skokie fire personnel responded to the call. They were assisted by Morton Grove police and the Niles Fire Department because at approximately the same time that Hennessy made his call, a fire alarm was pulled at Niles West, Miller said.

Police found Hennessy in the gym area of the school, where he was being attended to by an eyewitness to the incident.

Police would not say what type of events were being held at the school on Thursday night.

Police investigators were concentrating their efforts on the west side of the school where the entrance to the gymnasium and pool is located.

The Skokie Police Department is investigating the school grounds as a crime scene but school will be in session Friday, school officials said. Officials said crisis teams will be available for students and staff on Friday and next week.