LOS ANGELES - A $25,000 reward was offered Friday for information leading to the killer of two men whose bodies were found in a burning Mercedes-Benz last year, a unique case that police said involves a Playboy model and a $50 million Wall Street fraud.

Authorities say whoever killed Michael Tardio and Christopher Monson may have tried to rob them of more than $500,000 in jewelry that the two men planned to sell secretly - and illegally - for a friend.

The Los Angeles City Council offered a $25,000 reward for information leading to the arrest and conviction of the killer or killers. During a news conference at police headquarters, members of the victims' families asked for the public's help.

"The guy who did it is out there. Please try and help us find him," Tardio's brother, Neil Tardio Jr. of Pacific Palisades, said in a choked voice.

"A hole was blown in our hearts that can never be mended," said Irene Monson of Tucson, Ariz., the victim's mother.

"We are determined to find these people … we will never give up," she said.

She remembered the eldest of her five children as a man who loved to ski and ride motorcycles and was devoted to his family and friends.

"Many people thought that he was their best friend," said his father, Chris Monson. "And I think that's what, unfortunately, cost him his life.

"He would help people, and unfortunately in this case, he got in harm's way being a friend."

The rented Mercedes-Benz sport utility vehicle was found on fire about 1:30 a.m. Sept. 2, 2002, on a Studio City street. Tardio, 35, of Los Angeles, and Monson, 31, of Culver City, had been shot several times in the chest.

The fire probably was set to eliminate evidence, police said.

Some jewelry and other items were stolen and have not turned up, Detective Robert Bub said. He declined to provide details.

Tardio, originally from New York, was a Hollywood nightclub doorman and Monson, from Tucson, was a would-be actor who ran a self-storage company.

Detectives said they had driven to the San Fernando Valley to sell jewelry that belonged to Sandy Bentley.

A call and e-mail seeking comment from Bentley were not immediately returned Friday.

Bentley and her twin sister, Amanda, were on the cover of the May 2000 Playboy and she briefly lived with Playboy founder Hugh Hefner.

She received the jewelry from a former boyfriend, one-time Wall Street investment adviser Mark Yagalla. Authorities said he bought the jewelry with some of the $50 million he stole from clients and used to support a lavish lifestyle. He pleaded guilty last year to securities fraud and was sentenced to five years and five months in federal prison.

Federal authorities said Yagalla spent more than $6 million on Bentley, buying her six cars, three Rolex watches, a ruby and platinum necklace, other jewelry, furs and a Las Vegas mansion.

A court-appointed receiver trying to recoup some losses for Yagalla's victims demanded that Bentley turn over the gifts. The Los Angeles Times on Friday quoted court documents in which attorneys for the receiver claimed she initially refused "adamantly and with vitriol" but eventually did turn over some items.

However, investigators believe she kept jewelry worth up to $700,000 and persuaded Tardio, her boyfriend, to sell it.

Investigators believe Tardio and his friend had gone to make the deal with someone when they were murdered. Investigators believe that person probably robbed and killed the men.

"That is the strongest lead that we're working on," Bub said.

Bentley and Yagalla are not considered suspects in the killing.