Hours before he walked into his workplace and unleashed a barrage of gunfire that killed 12 people, the Virginia Beach gunman wrote his bosses a two-sentence email that said he was quitting for "personal reasons," according to a copy of the letter city officials released on Monday.

"I want to officially put in my (2) weeks' notice," DeWayne Craddock wrote. "It has been a pleasure to serve the city, but due to personal reasons, I must relieve my position."

The new document does not shed light on his possible motive nor provide insight into his frame of mind just before the rampage, but city officials view the letter as evidence that the suspect did not offer clues about his violent plans before carrying them out.

Julie Hill, a spokeswoman for the city of Virginia Beach, characterized the letter as "unremarkable," highlighting how it "contained no foreshadowing of the actions he would take later in the day."

Investigators are still searching for a motive in the shooting that ended with 11 government workers and one contractor dead and four others injured. The 40-year-old gunman, who had worked for the city as a civil engineer for nine years, was killed in a shootout with police. Among the dead were two supervisors in the gunman's city department, yet officials have stressed that nothing so far in the investigation suggests Craddock specifically targeted anyone. Instead, authorities say he unloaded dozens of rounds of bullets "indiscriminately."

Authorities say that in addition to carrying two .45-caliber handguns, the shooter had extended ammunition magazines and a device known as a suppressor that is supposed to muffle the sound of gunfire.

With law enforcement officials still puzzling over what set off the violence, the mood across sunny Virginia Beach has been grim at times.

Droves of mourners laid flowers outside an entrance of the municipal building in remembrance of the victims. Teddy bears, white crosses and other expressions of sorrow have accumulated into a manifestation of the community's grief.

Some have wondered if additional guards and metal detectors in government buildings would have made a difference, but standing near a memorial, Virginia Beach Mayor Bobby Dyer said the city's residents say this is not about increasing security.

"We can't let this horrible incident define us because you look at where people are vulnerable, movies theaters, malls, and everything, this is hopefully just an unfortunate anomaly," Dyer said. "We're going to go back to being Virginia Beach."

At another ceremony close by, dozens of Virginia Public School employees wore blue, the color of the city's flag and a nod to how central the ocean is to this beachside community, as way to pay tribute to those who were killed.

School Superintendent Aaron Spence, said he was struggling with the senselessness of the tragedy.

"We did not and could not imagine what happened on Friday," he said. "Fathers and mothers, daughters and sons, brothers and sisters, neighbors. Twelve people came to a building right next to ours on Friday and they did not return home. And they will never go home."

At a press briefing over the weekend, City Manager Dave Hansen told reporters the gunman was not forced to resign. Co-workers, Hansen said, did not express any concerns about Craddock before the shooting.

"He was in good standing within his department, and there were no issues of discipline ongoing," Hansen said.

Business will resume on Tuesday at the government complex where the violent attack took place. Officials say there will be a heavy police presence. At building No. 2, though, the yellow crime scene tape will stay, as federal investigators search it for additional evidence.

"There is an emotional challenge and a logistical challenge to all of this," the mayor said. "This is the start of a very long journey."

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