The gunman who killed 12 people at a Virginia Beach municipal building before dying in a shootout with police was identified on Saturday as a disgruntled city engineer and co-worker of most of the victims.

All but one of the victims from ­Friday's mass shooting in the coastal ­resort community were employed by the city, officials said, while the other was a contractor seeking a permit. Four people were wounded.

The gunman, DeWayne Craddock, had worked for the city's public utilities department for about 15 years, Virginia Beach Police Chief James Cervera said at a news conference. He declined to comment on any possible motive.

"These are 12 individuals who came to work ... thinking they would go home in the evening, and they didn't return and it left a tremendous void in their families and in our community," Virginia Governor Ralph Northam said at a news conference.

It was the worst mass shooting in the US since November 2018, when a dozen people were slain at a Los Angeles-area bar and grill by a gunman who then killed himself.

Bodies were found on all three floors of the Virginia Beach building and in a car parked outside, according to authorities.

Cervera described the crime scene as "horrific" and said that investigators who spent the night inside the building endured a "physical, emotional and psychological toll."

Police said the gunman was armed with two .45 caliber pistols and used an employee pass to enter secure areas before firing "immediately and indiscriminately" on victims while reloading with multiple extended ammunition magazines.

At least one of the pistols was fitted with a "sound suppressor," police said. Both handguns were bought legally by the shooter within the last three years, Ashan Benedict, a special agent at the US Bureau of Alcohol, Tobacco, Firearms and Explosives, told the news conference. Two more firearms were found at the home where Craddock lived alone, he said.

After the attack began, two police supervisors from a building across the street arrived within minutes, Cervera said, and they were quickly joined by two police dog-handlers. The suspect was killed after a lengthy gun battle.

The victims who worked for Virginia Beach had been employed for between 11 months and 41 years. Six worked in the public utilities department and five were employed in the public works department.

A number of vigils and commemorations are planned, including a memorial service the city is organizing for Thursday evening.

The bloodshed unfolded at Building Two of the municipal center complex on Friday afternoon as workers prepared to leave for the weekend. Some survivors recounted how they cowered in fear ­after stacking desks against office doors as makeshift barricades.

Three of the wounded victims were in critical condition and a fourth was in fair condition at local hospitals, said Julie Hill, a spokeswoman for Virginia Beach.

A police officer who was shot but saved by his ballistic vest has been ­treated and released, she said.