PHOENIX (Reuters) - The man suspected of killing six people in the Phoenix area, including a high-profile forensic psychiatrist, before committing suicide, used a legally owned .40-caliber handgun to shoot at least four of the victims, a law enforcement official said on Tuesday.

Dwight Jones, a suspect in a series of murders in Arizona, is shown in this photo provided June 4, 2018. Scottsdale Police Department/Handout via REUTERS

Dwight Jones, 56, killed himself on Monday as police closed in on the hotel near Phoenix where he was staying after a 72-hour shooting spree that left the region on edge. Among the victims was Steven Pitt, 59, who consulted on serial killings and the 1996 murder of child beauty queen JonBenet Ramsey.

Jones used the semi-automatic Glock pistol to kill Pitt and at least three others, said Thomas Mangan, a spokesman in Phoenix for the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Pitt was killed outside his office on Thursday.

Mangan said a check on the gun found that Jones was not the original purchaser, but he was lawfully allowed to have the weapon despite a 2009 arrest on domestic violence.

“It wasn’t a disqualifying prohibition for him to own, possess or purchase a weapon as far as we were concerned,” Mangan said in an interview.

The gun was recovered from inside a Scottsdale, Arizona, hotel room where Jones killed himself.

Investigators believe Jones may have been seeking revenge from what was a bitter, protracted divorce and custody battle.

In addition to Pitt, Mangan said the gun was used to kill paralegals Veleria Sharp, 48, and Laura Anderson, 49, and Marshall Levine, a 72-year-old counselor and psychologist.

Sharp and Anderson were killed in their legal office in downtown Scottsdale on Friday. Levine was found dead in his office on Saturday, police said.

Jones was also suspected of killing 70-year-old Mary Simmons and Bryon Thomas, 72, who were fatally shot inside an area home. Police have not yet said if the recovered Glock was linked to the double murder.

Jones, who police said lived the last nine years at extended stay hotels, took to YouTube weeks before the murders. In 18 videos where his face was never shown, he offered hate-filled rants about a legal system he said cost him his child, according to the state’s largest newspaper.

The Arizona Republic reported that in nearly 10 hours of footage, Jones railed against Pitt, his ex-wife, a judge, counselors and others connected to the case. The video channel has since been removed, it said.

Police said Pitt was involved in the divorce case, but have not offered further details about his role.