VIRGINIA BEACH, Va. (WAVY/AP) — A longtime city employee who shot and killed a dozen people at the Virginia Beach Municipal Center Complex on Friday had submitted his resignation that day.

Among the dead were four other engineers who worked to maintain streets and protect wetlands and three right-of-way agents who reviewed property lines. Others included an account clerk, a technician, an administrative assistant and a special projects coordinator. In all, they had served the city of Virginia Beach for more than 150 years.

Police Chief Jim Cervera said in a news conference Sunday morning that officers were on scene outside the building where the shooting happened within two minutes. Cervera said described the offices as a “honeycomb” and a “maze” due to renovations over the years.

Police identified the suspect as 40-year-old DeWayne Craddock, a worker in the public utilities department. He was allegedly able to shoot more than a dozen people before he was killed in an extended shootout with officers.

Cervera described how officers who entered the building pursued the man through a tightly packed warren of offices and exchanged gunfire with him. He did not know how many rounds were fired but said it was “well into the double digits.”

“In the police world, anything more than three to five shots is a long gunbattle,” he said.

At one point, the suspect fired at officers through a door and a wall and hit one officer, who was saved by a bulletproof vest. Then the firing stopped, and police realized the gunman was holed up in an office.

When they got into the office, they took the wounded shooter into custody and gave him first aid, Cervera said.

Cervera said there is no information at this point whether he was targeting anyone specifically. There was also no immediate indication why the man, a civil engineer, had notified a superior of his intention to leave his job in two weeks.

City Manager Dave Hansen confirmed in Sunday’s news conference that the suspect had sent his two weeks’ notice to his chain of command Friday morning. The assailant was an employee “in good standing” in his department, said Hansen said, who described the man’s performance as “satisfactory.”

Police have declined to comment on the gunman’s motive. City officials uttered his name just once and said they would not mention it again.

The guman’s family released a written statement on the front door of their home that said in part, “Our thoughts and prayers are with the families of those who loss their lives, and those recovering in the hospital.”

The deadly shooting led to an outpour of support from officials locally and nationwide, as well as neighboring localities in Hampton Roads. Virginia Beach City Public Schools Superintendent Aaron Spence asked everyone to wear blue on Monday in honor of the victim.

Both President Donald Trump and Virginia Gov. Ralph Northam ordered flags to be lowered to half-staff in honor of the victims.

City offices at the municipal center will be closed on Monday. Public schools and courts — along with other city offices outside the center — will operate on a normal schedule. Building 2 — where the incident took place — will be closed indefinitely, Hansen said.

Officials with Sentara Healthcare said Sunday morning four people remain in critical condition. Three of those people are at Sentara Virginia Beach General Hospital, while the fourth person is at Sentara Norfolk General Hospital.

Sentara said one of the patients at Virginia Beach General was fair but is critical due to “post-surgery recovery.” The patient at Sentara Norfolk is considered critical but stable.