Joseph Pappas, the trained marksman suspected of slaying one of former President George H.W. Bush’s doctors, killed himself when police confronted him Friday morning, Houston Police Chief Art Acevedo announced.

During a Friday morning press conference, Acevedo told reporters that the police were alerted to Pappas’ location Friday morning by a witness who works for the Houston Parks Board. After spotting him, the city employee found Pappas’ wallet on the ground, confirmed his identity, and reported his location to the police.

By 9:35 a.m., Acevedo said, an officer arrived at the scene. Pappas had his left hand raised and his right hand—his shooting hand—hidden. He ignored an officer’s commands to raise both hands. After a second officer arrived, Pappas pulled out his gun and shot himself in the head. He was pronounced dead on the scene.

During the press conference, Acevedo said the second officer’s presence was likely vital in de-escalating the situation. He noted that Pappas was wearing a bulletproof vest, and that “you don’t put on a bulletproof vest to commit suicide.”

“I’m convinced that if that second officer hadn’t arrived, there would have been a shootout,” he added, before noting that Pappas may also have intended to kill the Parks employee who reported him.

Acevedo revealed that when searching Pappas’ home late Tuesday night, officers uncovered a “very extensive intelligence file” that he had prepared on Mark Hausknecht, including his home, his job, and his car. “He knew everything he could possibly find on this man,” Acevedo said. Officers also discovered a one-page list of other employees at the Texas Medical Center, where Hausknecht worked before his death. Police alerted the medical center soon after the discovery.

Although Acevedo declined to call this list a “hit-list,” noting that it was extremely short compared to Hausknecht’s file, CBS Houston affiliate KHOU-TV also revealed this morning that Pappas may have had a different hit list, used to target a different set of lifelong enemies.

An unidentified source who knew Joseph Pappas told KHOU-TV that the “extremely intelligent” suspect had a list of enemies stretching all the way back to when he was bullied as a kid in high school—and he’d previously warned that each person on his list would meet “a day of reckoning.”

Little is still known about Pappas, but it has been confirmed that he was a former law-enforcement officer and a skilled marksman. After he allegedly gunned down Hausknecht while the doctor was riding a bike on July 20, Acevedo said: “There was a lot of planning that went into this. There was a lot of planning and, sadly, some skill.”

Acevedo said Pappas may have been seeking revenge for his mother, who died on Hausknecht’s operating table more than 20 years ago.

“I personally do not think the doctor is the only person that he is going to target,” said the anonymous friend. “I think [Hausknecht] was No. 1 on the list. And Joe [Pappas] is extremely intelligent. He’s patient, he’s unassuming, he’s a deadly shooter.”

The former friend added: “[When we were] hanging out together, over burgers and tacos, telling stories, he mentioned being called the ‘Greek shrimp’ in high school and said ‘Karma’s a real bitch,’ and one day the people who bullied him in high school would meet a day of reckoning.

“[When Pappas] made the comment, at the time I thought it was a joke, ‘Hey, don’t worry, you’re not on my list.’ Now, looking back on it, it makes me queasy to think, ‘Oh wait, maybe this guy has a list.’”

Before Pappas’ death, Houston Police officials said they couldn’t comment on the existence of a hit-list, or any tips they’ve received during the investigation.

Police say Hausknecht was shot three times—twice in the torso and once in the head—while riding his bike to work at the Texas Medical Center last month. They add that Pappas, who was also on a bike, was very fit—he managed to follow the doctor, pass him, then turned back and fired.

Five days after the fatal shooting, it’s believed the suspect tried to sell guns and ammunition online, though it’s not known if the items were used in the shooting. The items posted for sale included a semi-automatic rifle, a pistol, two bulletproof vests, and a bulletproof panel for a car.

In a sign that the murder may have been premeditated, the day before police say he shot and killed the doctor, Pappas transferred the deed for his southwest Houston house to a woman who lives in Ohio.

Before Pappas died, CBS asked the friend what he would do if he thought he was on the list. “If there’s a bully he had in high school,” he said, “I would tell that person to take an unplanned vacation to Alaska.”

During the Wednesday morning press conference, Acevedo thanked the community, and specifically the city employee, for their efforts in stopping Pappas from committing more murders, noting that “the community was our absolute greatest force multiplier.”

“This doesn’t bring anybody back, but this does bring closure to the community,” he added, before once again expressing his gratitude that no other innocent people were killed. “You don’t ever want to lose lives,” he said, “but if you have to lose someone, I’d rather it be the cold-blooded killer.”