Police had been searching for 49-year-old Dr. Timothy Jorden since Wednesday morning, when 33-year-old Jacqueline Wisniewski was found shot to death in a stairwell at the Erie County Medical Center.
The body was found Friday not far from Jorden's suburban home near Lake Erie.
Dennis Richards, Buffalo Police Department chief of detectives, said the man apparently died from a self-inflicted gunshot wound. An autopsy is being conducted.
SWAT teams had spent hours Wednesday searching the home without success.
"It's terrible," said Tom Wrzosek, a neighbor. "It's a tragic situation. Nobody wins in a situation like this."
Wrzosek had told police he heard a single gunshot from the steep, thick terrain behind Jorden's house on Wednesday morning, about 90 minutes after Wisniewski was gunned down at the hospital where she and Jorden worked.
Some of her friends told local media outlets that Jorden stalked her after she ended the relationship. One of her friends told WIVB-TV that Wisniewski told her the doctor had put a GPS tracking device in her car and once held her captive in her home for a day and a half, wielding a knife.
Jorden earned a medical degree from the University at Buffalo and trained at the Madigan Army Medical Center in Tacoma, Wash. He received his certification from the American Board of Surgery in 2004.
The Buffalo News reported that Jorden joined the National Guard in high school, went into the Army after graduation and served with the Army's special forces, first as a weapons expert, then as a medic. In those roles, he served in the Caribbean, Japan and Korea.
He was honored by various local organizations over the years for his teaching skills and involvement in the Buffalo community.
Jorden's colleagues told local media outlets that he had been acting strangely in recent months and lost as much as 75 pounds from his 6-foot-2, 250-pound frame.