The man who opened fire inside a dental office near San Diego was described as a “disgruntled” former patient who had legally armed himself two weeks ago, police said Friday.

Gunfire erupted at about 4:14 p.m. PST Thursday inside the practice at 480 N. Magnolia Ave. in El Cajon and responding police officers found two men and a woman had been shot, officials said.

One of those men died at the scene as suspect Mohammed Abdulkareem, a 29-year-old El Cajon resident, fled in a rented U-Haul pickup truck, authorities said.

“Investigations also revealed that Abdulkareem was a former patient of the dental office,” according to police. “While the exact motive behind the shooting remains under investigation, it is believed that Abdulkareem was a disgruntled former customer.”

Eye witnesses accounts helped police quickly find the U-Haul rental agency and description of the getaway vehicle, which was spotted by a bystander a little more than 15 miles southwest of the crime scene in San Diego, officials said.

The truck was empty and a “short time later, officers located Abdulkareem in the area and took him into custody without incident,” El Cajon police said.

The suspect was “armed with a loaded handgun and several loaded handgun magazines” and records showed that the weapon “was legally purchased by” him two weeks ago, police said.

Abdulkareem remained in custody on Friday, booked on suspicion of first-degree murder and two counts of attempted murder, jail records showed.

His arrangement was scheduled for Tuesday and it wasn’t immediately known Friday if he had hired or been assigned a defense lawyer yet.

This article was originally published on NBCNews.com