There was something strange about the man seated in the lounge chair at the end of the pool.
He kept quiet, staring straight ahead, while more than two dozen people sipped drinks and barbecued during a 50th birthday party on a pleasant San Diego afternoon.
Demetrius Griffin, 25, took note of him.
"It was really hot outside. And he had on kind of a jacket, and a T-shirt under the jacket and some cargo shorts. No computer, no book," said Griffin, who had flown in from Seattle to attend the party.
The man who was celebrating his birthday Sunday decided to head up to his apartment to grab some more food and drinks for his guests. According to Griffin, the host passed by the quiet man and appeared to say something but got no reply. So he kept walking.
Then the quiet man placed a gun on his lap, Griffin said.
Over the next several minutes, according to witnesses and police, 49-year-old Peter Selis shot seven of the partygoers — one fatally — before he was killed by San Diego police.
During a press briefing Monday, Police Chief Shelley Zimmerman said that Selis was despondent over a recent breakup and had called his ex-girlfriend during the shooting rampage.
"What started as a celebration of a friend's birthday turned into a tragedy of epic proportions," the chief said.
The fact that Selis was white and his victims were either African American or Latino fueled speculation that the attack may have been racially motivated. But Zimmerman said there was ""zero information to indicate that race played a factor."
The woman who died was identified Monday as Monique Clark. Two of the victims remained hospitalized in critical condition, Zimmerman said.
According to the chief, Selis walked to the pool area about 6 p.m. Sunday and sat in a lounge chair. He opened fire from there, then walked around the pool as he continued to shoot off round after round.
At one point, Zimmerman said, Selis told his ex-girlfriend he had just shot two people. "It is apparent that Selis wanted his ex-girlfriend to listen in as he carried out his rampage," the chief said.
The first to be shot, Griffin said, was the guest of honor — who spent his birthday Monday in the hospital after undergoing two surgeries. He was listed in stable condition.
As Selis turned his gun on the crowd, Griffin said, people ran in panic. Griffin tried to flee, but the shock of what was happening left him paralyzed.
"I kind of froze because I didn't believe it was real," Griffin said.
When he took off running seconds later, Griffin said, he noticed a woman who had been shot in the legs screaming for help. He and another man dragged her to safety, then Griffin took his shirt off and wrapped it around the woman's wounds in attempt to stop the blood.
A resident at the upscale La Jolla Crossroads — in an affluent pocket of the city about two miles from the UC San Diego campus — told KFMB-TV that he had been in his apartment when he heard a series of gunshots and screams. He ran to the building's clubhouse, from which he could see the pool.
The shooter, who also lived at the complex, seemed at ease, the witness said.
"He had his beer in one hand and his gun in the other," he said. "There were two victims lying on the ground, one trying to crawl toward the other one to help."
Police received multiple 911 calls at 6:06 p.m., and 20 officers and a police helicopter arrived within minutes, Zimmerman said.
Officers in the helicopter saw Selis standing in the pool area, reloading a large-caliber handgun. As he was approached by a San Diego police sergeant and two patrol officers, Zimmerman said, he shot at them before advancing and pointing the weapon in the officers' direction.
All three returned fire. Selis was pronounced dead at the scene.
Selis, who court records show was married with two children and a stepson, was having severe financial problems.
He owed thousands to a number of different medical centers in the San Diego area, and had been subject to claims from a number of credit card companies, according to a 2015 bankruptcy filing. In total, he appeared to be carrying more than $100,000 in debt.
Records also show that Selis had worked as a mechanic at a San Diego Ford dealership since at least 2010. A photo of him on the dealership's website shows a broad-shouldered man with a receding hairline, wearing a half-smile.
On Monday, Zimmerman said that Selis did not have any criminal history. He had legally purchased a .45-caliber Sig Sauer handgun three years ago, the chief said, but she did not specify if that weapon was the one used in the attack.
According to Griffin, Selis did not utter a word before opening fire.
"All it's ever gonna be is speculation," he said of Selis' motivation. "What I am gonna say is, this is an act of terror, not necessarily an act of terrorism."
Parvini reported from San Diego and Queally and Hamilton from Los Angeles. The San Diego Union-Tribune contributed to this report.
6:45 p.m.: This story has been updated with additional details.
2:20 p.m.: This story has been updated with details from a witness who attended the party and was friends with many of the victims.
11:30 a.m.: This story was updated with additional details from San Diego police.
8:20 a.m.: This story was updated with comments from Rep. Scott Peters.