The incident happened at a shopping center on Route 202 in Bridgewater Township just before 5 p.m. Monday.
55-year-old Roy Devoe, the owner of Roy T. Jewelers, was shot to death.
Police say the suspect, 19-year-old Michael J. Koury of Bridgewater Township, entered the front door of the shop disguised.
Detectives say that immediately upon entering, the gunman brandished a .357 caliber Smith and Wesson revolver and confronted the adult daughter of the store owner.
The gunman demanded jewelry and threatened to shoot the daughter if she didn't cooperate.
Mr. Devoe then confronted the gunman who fired one round from the revolver striking Mr. Devoe in the head and fatally wounding him.
The gunman then turned his attention towards the daughter and fired a round at her as she fled from the jewelry store.
The gunman turned the gun on himself firing one round into his jaw causing significant injuries to the lower portion of his mouth. He then cut his throat by utilizing a stainless steel 9" knife which he previously had secured in a plastic sheath strapped to his right thigh. The gunman then fired one last round into his head ending the deadly ordeal.
The revolver and the knife were recovered at the scene next to the gunman.
The prosecutor says Koury left a suicide note at his home.
The incident has left residents stunned and upset.
Broken glass, heavily armed police and yellow tape mark the scene of the crime.
Fae Cushings had been in the store at about 3:45 p.m. Monday. An hour later, she said, and she could have been among the dead.
"If I had been there an hour later, that would be us," she said. "I am so feeling for the people inside."
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