NEW YORK, July 23 (UPI) -- New York police say a gunman who died in a Staten Island shootout had escaped from a psychiatric hospital less than an hour earlier.

Former New York City police Sgt. Jason Aiello was killed Tuesday after opening fire on officers in front from his SUV parked in front of his home about 30 minutes after he fled the hospital, police told the New York Post.

Aiello had retired from the department and became a bodyguard for a jeweler who was killed in April in what the FBI suspects was a mob-ordered hit. The Post said Aiello had come under suspicion of having played a role in the jewelers' slaying.

"The investigation was weighing on him more than you can imagine," said Doug Miglino, his cousin. "It was killing him."

Aiello's mother told the newspaper her son feared he was having a nervous breakdown.