An employee at a suburban New Jersey supermarket opened fire in the store in the pre-dawn hours on Friday, killing two co-workers and then taking his own life, a prosecutor said.
The 23-year-old shooter, who had not yet been identified, was on a night shift at the Pathmark grocery when he left the store at about 3:30 a.m. EDT (0730 GMT) and returned shortly after with an AK-47 and a handgun, Middlesex County Prosecutor Bruce Kaplan told a news conference.
Shots were heard inside the supermarket in Old Bridge, about 35 miles from New York City, just before 4 a.m. EDT (0800 GMT) as employees were preparing to open the store for business.
The two victims, identified as an 18-year-old female and a 24-year-old male, were Pathmark employees and were among a dozen workers in the store at the time. They were shot in separate areas of the store, Kaplan said.
"He entered the store firing his weapons," and magazines were found scattered around the store, Kaplan said.
The incident comes just one week after an unemployed New York City man shot and killed a former co-worker near the Empire State Building before being shot dead by police.
In July, a gunman opened fire in a crowded Colorado movie theater, killing 12 people, and earlier this month a white supremacist opened fire in a Sikh temple in Wisconsin, leaving seven people dead.
Old Bridge Mayor Owen Henry described the suspected shooter as a former marine and a disgruntled worker who had been employed by the Pathmark for just a few weeks, the Star-Ledger newspaper said.
"This is the worst phone call a mayor can receive," Henry told the newspaper. "You can prepare for these things but you can't prevent them."
Kaplan said he could not confirm details about the shooter beyond his age.
Hours after the shooting, the store remained closed and police had blocked off one of the roads leading up to the shopping plaza that houses the Pathmark.
Local residents expressed shock that violence had come to their community.
"It's a quiet neighborhood," said Maritza Hernandez, whose daughter works as a cashier at the Pathmark but was not at the store when the shooting occurred.