A manhunt was underway Wednesday for a shooter who opened fire during a house party in Long Beach, leaving three people dead and nine others hospitalized.

Officers responded to a shooting call at a residence in the 2700 block of Seventh Street, near Temple Avenue, in the Rose Park area about 10:45 p.m. Tuesday. Three victims were confirmed dead at the scene and nine others suffered gunshot wounds, some considered life-threatening, police said.

"The crime scene is horrific; there's blood everywhere," Long Beach police Chief Robert Luna told reporters at a briefing this morning.

Luna said the three deceased victims were men and the wounded included seven women and two males. He had no updated information on their conditions.

Homicide investigators determined there was one shooter, "a man wearing dark-colored clothing with his face concealed," who appeared to fire indiscriminately into the crowd of 25 to 30 people, according to Luna.

The shooter fired from an alley behind the residence and fled in a dark-colored vehicle, according to police, who did not give a motive for the attack.

Police identified the wounded victims as a 20-year-old woman from Anaheim, a 27-year-old woman from Hawthorne, a 27-year-old man from Cudahy, a 28-year-old woman from Los Angeles, a 28-year-old woman from Gardena, a 29-year-old man from Hawthorne, a 30-year-old woman from Compton, a 32-year-old woman from Lawndale and a 49-year-old woman from Los Angeles.

Their names were withheld.

Luna said most of the victims lived outside Long Beach and worked together at a business he declined to name.

The man who rents the home where the shooting occurred told the Long Beach Post that his son had been hosting a birthday party for one of his co-workers. Chan Hou said his family was safe, but some friends were killed.

Luna said the county coroner's office was working to notify the fatally injured victims' families.

"That's not a job anyone wants to do," the chief said. "Can you imagine your loved ones go off to a party and the next thing that happens is you get a call from the coroner telling you your family member is dead? It's heartbreaking."

Luna said dozens of personnel were involved in the investigation.

"Our homicide detectives are on the scene searching for clues to the gunman," he said. "They're also searching the neighborhoods around the shooting for any cameras or video footage that will help us identify the coward or cowards who did this shooting. What kind of coward walks up to an apartment and starts firing into an apartment full of people indiscriminately?"

Luna asked the public to call police with any information that would be helpful to the investigation.

"I know someone out there knows something that can help us. Please call us," he said, telling reporters he doesn't believe "this was a random act of violence."

"This is a horrific and sad day in our city,'' Mayor Robert Garcia tweeted Wednesday. "We have 3 dead and multiple injured in an act of tragic gun violence. The LBPD is working hard -- please keep the victims and their families in your thoughts."

At 6 p.m., City Councilwoman Jeannine Pearce will host a vigil for the victims at St. Matthew Catholic Church at 672 Temple Ave., which is less than a block from the shooting scene.

"Our hearts go to each individual present and their families,'' she said in a Facebook post.

California Sen. Kamala Harris tweeted: "My heart goes out to the victims of the Long Beach shooting and the heroic first responders who were on the scene. This gun violence shouldn't be commonplace."

Anyone with information was asked to call Long Beach Police detectives at 562-570-7244. Tipsters can also call Crime Stoppers at (800) 222-TIPS.