A gunman killed two people early Friday at a Pathmark grocery store in Old Bridge, N.J., before taking his own life, the city's mayor said.

The gunman was believed to be a disgruntled employee who had been working at the store for about two weeks, The (Newark) Star-Ledger reported.

The attack occurred around 4 a.m. EDT.

"This is the worst phone call a mayor can receive," Mayor Owen Henry told the newspaper. "You can prepare for these things but you can't prevent them."

The gunman is a former Marine, Henry said. The man was working at the store Thursday night but left and came back armed with an AK-47 assault rifle and an automatic pistol.

The man's name has not yet been released.

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