An independent auditor on Wednesday released a four-month study of the shooting rampage at the Virginia Beach municipal center in May, but the report still leaves victims’ family members, city leaders and the community wondering why a city engineer decided to open fire at his workplace.

In July, city officials hired the risk management firm Hillard Heintze to examine the city’s response and workplace factors that may have led DeWayne Craddock to kill 12 people just hours after he submitted his resignation in an email.

The firm reviewed 335,000 emails and 6,500 documents, conducted interviews with city managers, held listening sessions with employees and scoured Craddock’s life in search of clues that may have indicated danger.

The report said the gunman did not display warning signs that may have allowed the city to intervene before the May 31 attack. It also found nothing to substantiate widespread rumors of an employee who was denied promotion or was aggressive in the workplace.

“I think when you say why, everyone wants a nice, clean reason. Those clear answers don’t exist here,” Debra Kirby, the firm’s senior vice president, told city leaders at a meeting Wednesday.

In its probe, Hillard Heintze described purchases by Craddock of several handguns, body armor and a noise suppressor. Searches of Craddock’s cellphone revealed “at least five queries to websites that contained news about mass shootings between May 2018 and May 2019,” the report stated.

The report said that he had stressors in his life such as a divorce and criticism of his job performance, but nothing that would indicate a predilection to a violent outburst.

“What seems to be puzzling to me is that we just don’t have enough information about the attacker,” city council member Sandra Wooten told the report’s authors.

Hillard Heintze CEO Arnette Heintze described Craddock as a loner at work. City records showed that Craddock was placed on a performance improvement plan and had written drafts of emails that expressed that he felt unfairly treated. But Craddock never sent those emails, and there was no indication his managers knew of them, Heintze and Kirby said.

In the report, released Wednesday, consultants gave details about a conflict Craddock had with the city’s purchasing department. The May 29 incident involved a vendor invoice for about $3,000 that Craddock was not authorized to approve. Craddock received a voice mail from the city’s procurement department stating, in part, that his conduct had violated a city ordinance. A supervisor said Craddock had a negative reaction to the voice mail, and a co-worker also said he was upset by it, the report said.

A supervisor told investigators the incident would not have led to Craddock’s being fired and that he was on the path to “meet expectations” at his evaluation in August.

On May 30, Craddock called both his mother and his ex-wife, the report said. His mother said he complained about insomnia and his work supervisors but otherwise seemed upbeat and discussed the future.

He also had a 40-minute conversation with his ex-wife, to whom he had not spoken in some time. His ex-wife described Craddock as amicable and said he stated that he wanted them to remain friends.

The auditors cautioned that they did not have access to Craddock’s personal computer or records, which are being examined by the FBI and may hold clues to his thinking.

Jason Nixon, whose wife, Kate, was killed in the rampage, said that he is “disgusted” by the review because he thinks the city limited the scope of the auditors’ work.

He insists that his wife and others had complained about Craddock’s behavior, and that Kate had copied supervisors on emails she had sent about him.

“They knew for two years this guy had issues,” Nixon said. “HR did nothing; his direct supervisors did nothing.”

Nixon said he’s looking to the FBI for a more thorough investigation.

The Hillard Heintze report is the second investigation into the rampage. In September, a police investigation described Craddock’s movements immediately before the shooting, but it, too, did not identify any factor that could have prompted the attack.

In its 262-page report, Hillard Heintze also described heroic acts by city employees on the day of the shooting and listed nearly 60 recommendations of changes the city should make in areas such as human resources and safety strategies for city buildings.