ORINDA — Four people were killed and at least four others injured in a shooting during a packed Halloween party at a rented Airbnb mansion, shocking the affluent bedroom community where homicides remain exceedingly rare.

“We are focused on the four people who have lost their lives, their families, and the other victims of this tragedy including the four other people who have been wounded,” Orinda Mayor Inga Miller said. “Our Orinda police are focused on finding the parties responsible.”

Early Friday morning, officers had blocked off the curving hill leading up to the four-bedroom home at 114 Lucille Way, while at least five police cars lined the road, including San Francisco police. Members of the Contra Costa County Sheriff’s Office search and rescue team canvassed the scene with metal detectors.

Orinda police Chief David Cook described it as a “chaotic scene” and that witnesses are still being interviewed. The investigation is still in its early stages, and police have not even confirmed how many shooters there were.

“We’re still trying to wrap our arms around what exactly what transpired,” Cook said.

No suspects have been arrested.

Cook said officers responded to a call around 10:45 p.m. Thursday for shots fired at a short-term rental. The property had been reported for large parties before, but had not been on the city’s radar for months, officials said.

“(The owners) were every receptive. They were very cooperative and they said they would comply. Up until last night it appeared they had complied, City Manager Steve Solomon said. He added that no more than 13 people were supposed to be at the property, per city regulations.

“This event exceeded that,” Solomon said.

When officers arrived, they found a party with more than 100 people in attendance at the house, as well as three people who were pronounced dead at the scene and four others who suffered injuries, Cook said. No information was immediately available on victims’ gender or ages.

As police arrived, they observed dozens of attendees running from the home, police said. Some eyewitnesses were interviewed.

“These was a lot of noise and yelling and people running,” Cook said.

The fourth victim was pronounced dead at John Muir Medical Center in Walnut Creek, said spokesperson Ben Drew. Three other injured people were also transported to the facility; one is in critical condition and a second in serious condition, while the last was treated and released.

The total number of injured people has not been confirmed, said Contra Costa County Sheriff’s Office spokesperson Jimmy Lee, because some transported themselves to receive medical treatment.

Romand Reynolds, of Vallejo, said his 24-year-old son Armani mentioned that he was going to a Halloween party on Thursday night “and the next thing I know he was shot” three to four times.

Friends drove Armani Reynolds to a local hospital, and he was later transferred to Highland Hospital in Oakland where he remained in a coma late Friday morning, his father said. Romand came to the blocked-off scene on Lucille Way on Friday morning to try to retrieve his son’s car.

“As far as I know, he was a victim,” Romand said. “He was just at the wrong place at the wrong time.”

It’s the largest number of homicide fatalities in the city in recent memory: Orinda’s last homicide was in 2012, Miller said, when a man killed his longtime girlfriend; previously, a killing had not taken place for at least a decade, police said.

The home where the party took place is located via narrow, winding streets, lined with multi-million-dollar homes, on a hill southwest of downtown Orinda. Made up of around 19,000 people, the city is located in central Contra Costa County and known to be a quiet bedroom community.

Property records list the owner of 114 Lucille Way as Michael Young Wang, with an associated 2005 purchase price of $1.25 million. The home spans 3,972 feet. Residents from four homes in the neighborhood said he never appeared to move in or live there; records show that Wang’s primary residence is in Concord.

Several hours after the shooting, the streets were in darkness as a group of cars wound their way up and parked on a street as close as possible to the crime scene. People in the cars got out and huddled together, with some crying. They appeared to have been at the party or to know some of the victims. A woman in the group told a reporter they did not want to talk. The group left a short time later.

As the sun came up Friday morning, residents rushed to get their children off to school or to get to work. Several expressed shock. Jennifer Schreiber, who grew up in a house up the street and who was visiting her mother who still lives there, said, “It’s great here. We’ve never had any issues. It’s always been quiet.”

Other area residents say the house was known for large, rowdy parties and that neighbors had complained to police. There was one hit and run at a previous party, and another incident where a liquor bottle was thrown into an adjacent property, according to two residents who did not want their names used.

“It is definitely known as a party house,” said one neighbor who declined to give his name.

Cook said the house was being rented by people “not from Orinda.” He declined to elaborate.

Miller said the City Council will “discuss the issue of short-term rentals” at its next meeting, an indication the city may consider restrictions on such rentals within city limits. The council cannot take any action at its Tuesday meeting, because the Brown Act forbids it. Miller said some regulations, including a limit on rentals, are already in existence.

Miller said that the city of Orinda issued a “notice of violation” to the owner in February for having more people at the property than allowed for a short-term rental, but there have not been more reports of occupancy violations again until last night.

According to social-media posts, an “AirBNB mansion party” had been advertised for Thursday night. The flier was adorned with crime-scene tape and told attendees to “DM for location,” “BYOB” and “BYOW.” One post sharing the flier appeared to have a location of “Orinda, California” and said doors would open at 10 p.m.

“We are horrified by this tragedy and are in close communication with Chief David Cook of Orinda Police to offer our support with his investigation into who committed this senseless violence,” said Airbnb spokesperson Ben Breit.

The company has banned the person who booked the house from the Airbnb platform, Breit said, adding that parties were specifically prohibited in the property listing.

Neighborhood resident Willie Yee said he was watching the news late Thursday night when he heard “dozens” of people running in a panic for their cars.

“I thought it was a sideshow,” he said. “I knew right away this wasn’t anything ordinary going on.”

The town is generally so quiet, Yee said, “the people don’t call it ‘Bor-inda’ for nothing.”

Even so, it’s not the first time that Airbnb parties have made headlines in Orinda. Back in 2016, a party at a short-term rental on Camino Encinas led to a brawl, leaving one man in critical condition.

The following year, the city passed an ordinance requiring residents to register with the city if they wish to offer their home as a vacation rental through Airbnb and other services, plus abide by various regulations.

Halloween parties, often festive affairs, have seen striking upticks of fatal violence last year and this year. In Long Beach this week, three men died and nine others were injured late Wednesday during a joint birthday party and Halloween party. In an off-campus college party last Sunday in Greenville, Texas, two people were fatally shot and 12 others injured. Last year, a private Halloween party in East Palo Alto left two men dead and two others critically injured.

The flags at City Hall and other municipal locations have been lowered to half-mast, Miller said, calling it a “somber” day for the city.

“This is a tragedy of unimaginable gravity,” she said.