The body of Sang Ho Kim, who authorities believe entered a Garden City business and shot two people, one fatally, over an apparent business dispute, was found earlier this week.
Investigators say Kim shot himself in the mouth. Officials say the 63-year-old had heart disease and drowned.
Kim fled after the shooting, prompting a lockdown at the Roosevelt Field Mall and a lockout at several area schools. His car was found later in Cold Spring in Putnam County.
Kim's sister says he contacted her after the shooting to say he planned to commit suicide.
The body was found early Monday on Iona Island, part of Bear Mountain State Parkway, which is patrolled by New York State Park Police.
At about 8:30 a.m., a recreational boater aboard a sailboat spotted Kim's body in the river just south of the Bear Mountain Bridge, near the Rockland County shoreline, authorities said.
Hours later, the medical examiner's office identified the body.