Law enforcement in San Diego searched for clues Monday about why a man went on a deadly shooting rampage at a pool party.
The shooter, identified by authorities as 49-year-old Peter Selis, looked "relaxed," a resident told CNN affiliate KGTV, when he opened fire, killing a woman and wounding six others on Sunday evening.
"We could see the shooter sitting there with a beer in one hand and a gun in the other."
Selis took aim at people in a pool area at the La Jolla Crossroads apartments, authorities said.
As police responded to 911 calls, officers flying above the complex in a helicopter could see the suspect in the pool area, and he appeared to be reloading a large-caliber handgun, officials said.
Three officers who raced to the scene confronted the shooter, who pointed his weapon at them, prompting an exchange of gunfire, police said.
Police officers shot and killed the gunman, authorities said.
"This was a truly horrific and disturbing act. We pray for the victims and thank our first responders. Our city rejects this senseless violence," San Diego Mayor Kevin Faulconer said at a news conference.
Shots ring out in placid neighborhood
The upscale complex is located near the University of California San Diego campus and the shooting rang out in what is normally a tranquil location.
Enzo Zhuang, a student at the school whose apartment overlooks the pool, was playing video games when he heard arguing and minutes later, noises that sounded like fireworks.
"I thought to myself, who would be lighting fireworks?" Zhuang said, adding,"it was always peaceful here before this happened."
Gabrielle Sulli, who lives at the apartment complex, told KGTV heard "people screaming" and said "there is a crazy guy that is shooting, we decided to run ... we literally saw people jumping out from the fences and running away like crazy."
In a span of about 30 minutes, apartment residents heard gunfire, sirens and the screams of those near the main pool, said resident Susan Berry, who was at the property but did not witness the shooting.
Video from the scene showed ambulances, yellow police tape and a heavy police presence. Berry said those things aren't a common sight at the complex, which college students, physicians and military families, among others, call home.
"People are shocked because it's an affluent neighborhood," Berry said.
The gunman was a white. The victims were identified only as four black women, two black men and a Hispanic man. Their names were not immediately released.
It's not clear whether Selis knew any of the victims, police said. Detectives have not determined the motive for the shooting.
Another person was injured in the incident, breaking his arm while fleeing the gunfire, police said. San Diego police chief Shelley Zimmerman initially said eight people had been shot. Some of the injured were in critical condition late Sunday night, police said.
Selis, who faced significant debts, filed for bankruptcy in 2015. He listed his occupation as a car mechanic, according to a petition filed in US Bankruptcy Court in the Southern District of California.
Some of the people at the pool were celebrating a birthday, police said. It's not clear exactly how many people were in the pool area at the time of the shooting.
Police said they believe Selis and at least one of the partygoers lived at the apartment complex.