Twelve people were killed and five others injured inside the Virginia Beach Municipal Center on Friday afternoon when a long-time city employee fired on them.

The shooter, an employee of the public utilities department, opened fire shortly after 4 p.m. on multiple floors of the building, which houses the city's utilities and public works operations.

The man was shot dead by officers who engaged with him; his name has not been released. One officer was shot during the exchange, but was saved by his bulletproof vest, Police Chief James Cervera said.

One officer was shot during the exchange, but was saved by his bulletproof vest, Police Chief James Cervera said.

"I can tell you that it was a long gun battle between those four officers and that suspect," Cervera said. The building houses over 400 workers.

Several agencies including the FBI have launched investigations into the shooting.

President Donald Trump had been briefed and was monitoring the situation, Fox News reported.

"This is the most devastating day in the history of Virginia Beach," Mayor Bobby Dyer told reporters.

This article is originally published on IBTimes US.