Local officials are offering $30,000 to help capture the killer or killers who left three dead and nine injured at an Oct. 29 party in Long Beach’s Rose Park neighborhood.

The Los Angeles County Board of Supervisors and the Long Beach City Council each voted Tuesday to contribute $15,000 as a reward for information leading to an arrest in the case.

Police say there was at least one suspect, a man wearing dark clothing with a mask concealing his face, who fled the scene in a dark-colored vehicle after shooting at partygoers in a backyard in the 2700 block of 7th Street.

Maurice Poe, Sr., who lost his son in the fatal shooting 7 days ago at a halloween themed birthday party, lights incense during a memorial ceremony in Long Beach on Tuesday, November 5, 2019. The house where the tragedy occurred was opened to the community and a group of Buddhists Monks lead prayers for the souls lost and those injured. (Photo by Brittany Murray, Press-Telegram/SCNG)

Yellow and red tarps sit on the front lawn of a house on Wednesday, Oct 30, 2019, where a shooting during party the night before in Long Beach, CA. The shooting left three men dead and nine other people injured with the shooter at large early Wednesday. (Photo by Jeff Gritchen, Orange County Register/SCNG)

Chanchenda Hou, father of Daniel Chan, cries as he recalls seeing all the blood after the Halloween themed birthday party ended with 3 dead and 9 injured at their home Tuesday night. Hou wants to bring in monks to pray for the lost souls and he wants to move out of the house that now has too many images for him, Long Beach on Thursday, October. 31, 2019. (Photo by Brittany MurrayPress-Telegram/SCNG)

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Daniel Chan, 27, hosted the Halloween themed birthday party ended with 3 dead and 9 injured in the 2700 block of 7th street on Tuesday night. Two days after the horrific event he and his best friend Pam Sipraseuth, left, who was also at the party, are still in shock and trying to stay strong, in Long Beach on Thursday, October. 31, 2019. (Photo by Brittany MurrayPress-Telegram/SCNG)

Long Beach Police Chief Robert Luna spoke to reporters early Wednesday, Oct. 30, 2019 about a shooting that left three people dead and nine injured the night before. (Photo by Brittany Murray/SCNG)



L-R Commander Erik Herzog and Police Chief Robert Luna look over the gate at the scene of a shooting that killed 3 and wounded 9 Tuesday night in the 2700 block of 7th Street near Ohio Avenue in Long Beach on Wednesday, October. 30, 2019. (Photo by Brittany MurrayPress-Telegram/SCNG)

About 100 people gather for a vigil at St. Matthew Catholic Church for the 12 shooting vicitms in Long Beach on Wednesday, Oct. 30, 2019. A shooting at a party Tuesday left three dead and nine wounded. (Photo by Scott Varley, Daily Breeze/SCNG)

The house which sits behind a nail salon was the scene of a shooting that killed 3 and wounded 9 Tuesday night in the 2700 block of 7th Street near Ohio Avenue in Long Beach on Wednesday, October. 30, 2019. (Photo by Brittany MurrayPress-Telegram/SCNG)

A shooting at a Halloween event in Long Beach on Tuesday night injured 12 people, three fatally, the Long Beach Fire Department said. (Photo by OnScene.TV)

Over the years, there hasn’t been a lot of research on whether monetary rewards are successful, but a Chicago-based criminologist has spent a lot of time trying to figure out if they are.

“From a scientific standpoint, there is no solid evidence that offering a reward increases the overall likelihood that a crime will be solved,” said Arthur Lurigio, a professor at Loyola University Chicago. “My common sense and intuition – put aside my being a scientist and psychologist – I would think, ‘Of course that should make a difference,’ because you’re providing a financial motivation.”

But there are a lot of factors when people consider approaching police, including if the suspect is a relative or they otherwise know him or her – or perhaps they have been partners in crime.

“If people were going to report to the police and felt safe enough to report it,” Lurigio said, “they probably would’ve, otherwise I don’t know if the money could be the tipping point for them.”

Then again, there isn’t a lot to lose in offering a reward.

“It’s the community’s way of expressing their outrage,” Lurigio said.

At first rub, having a lot of witnesses seems like a real good thing: There were 25 to 30 people attending the joint birthday and Halloween party that night in Long Beach. But solving cases evolving from a violent party can breed problems.

“In any shocking event, many things can affect eyewitness memory,” said Elizabeth Loftus, a psychologist at University of California, Irvine and an expert on memory. “But when you have people who are intoxicated, it adds an additional level of concern. Alcohol affects the formation of new memories. People can form poor memories while they’re intoxicated.”

In April 2015, Ruben Sosa, 27, was at a house party in Oakley in Northern California when he was shot and killed during a large fight outside the home. There were dozens of eyewitnesses, but no one has been charged yet in Sosa’s killing.

About 35 miles away in Orinda, at least one gunman killed five this past Halloween evening as 100 others were about at a party in a rented mansion. Police have not announced an arrest so far.

“Well, obviously there’s the issue that it was Halloween and people are going to be in (costumes) and alter their appearance,” Qiana Washington, a defense attorney based in Walnut Creek, said about that case. “If people are intoxicated, that’s going to impair their memories. …

“And then, when you have shootings happening, people are going to focus on survival,” Washington said. “They’re not going to be studying who’s shooting; they’re just going to be trying to protect themselves.”

Police asked that anyone with information on the Rose Park shooting call them at 562-570-7244 or anonymously leave a tip with Crime Stoppers at 1-800-222-TIPS (8477) or by texting “TIPLA” plus a message to 274637.