A Playmate, a Ponzi scheme, jewels and murder

"48 Hours" investigates two unsolved Hollywood murders and the trail that leads through the Playboy Mansion and Wall Street

Produced by Chris O'Connell, Ira Sutow and Greg Fisher

[This story originally aired on Feb. 19, 2011.]

HOLLYWOOD, Calif - Retired Los Angeles homicide Detective Bill Cox says he is haunted by the unsolved murders of Michael Tardio and Chris Monson, two handsome young men who had come to Hollywood to chase their dreams.

"I think about it quite a bit more than I should," Cox says. "In all my 20 years of working homicide, I have never run across a case like this one!"

It's a case that has frustrated police in Hollywood since 2002. Which is why this week, "48 Hours" brings you a very different mystery. There's no trial to see, not even an arrest. But Det. Bill Cox and other investigators remain convinced this double homicide can be solved - perhaps with your help.

The story begins with what "48 Hours" has learned about this crime and its two victims: Michael Tardio, 35, a part-time model and doorman at the Garden of Eden - at the time, Hollywood's hottest nightclub - and his friend, Christopher Monson, 31.

"Both young men came from successful families," according to Los Angeles Times crime reporter Andrew Blankstein. "Michael Tardio ... He's kinda living the fast life."

"You know, just a clean-cut looking guy," Det. Cox tells "48 Hours Mystery" correspondent Peter Van Sant. "He was well liked... Maybe he just hadn't found his way, yet..."

"Chris Monson comes from a pretty tight-knit family," Cox continues. "They had some storage facilities that they owned."

"...Chris Monson is in Los Angeles running the family's business, here," Blankstein explains. "By all accounts Tardio and Monson were close friends and hadn't been in trouble with the law."

This made the events on the morning of Sept. 2, 2002, so shocking. The bodies of Michael Tardio and Christopher Monson were found in a luxury SUV. They had been shot at close range. The killer or killers tried to burn the vehicle.

Cox says it appeared they had been executed.

"There was no identifiable fingerprints found on there - there was no really useable evidence," he says.

Detective Cox took "48 Hours" to the upscale North Hollywood neighborhood where the SUV was discovered.

"None of the people that lived in the neighborhood had heard any shots at all," he tells Van Sant.

"It's not the kind of place that you're gonna find two people murdered on the street," Blankstein points out. "And so the theory is that the two men were shot somewhere else and then brought to that street where the car was later lit on fire."

As investigators dug into the victim's backgrounds, they discovered that Michael Tardio had a girlfriend that most men could only dream of - someone millions of men had seen naked: Sandy Bentley, a Playboy cover girl and former live-in lover of the world's most famous bachelor, Hugh Hefner.

"She's one of the kind of first wave of post-divorce Hugh Hefner women who are living at the mansion....while he's single and sowing his oats," says Blankstein.

Sandy, and her identical twin sister, Mandy, had their 15 minutes of fame back in 2000 as "The Bentley Twins." They lived with Hef at the Playboy Mansion, sharing his famous circular bed and sharing some air time as well, appearing on some of television's most popular shows, like "Sex and the City," "The Daily Show with Jon Stewart" and on "Two and a Half Men," where they played party girls.

"Hef had a thing for twins... I think Hef loved Sandy. I definitely think that he was genuine about his feelings," says Izabella St. James, another former live-in Hef girlfriend who wrote about life at the Playboy Mansion in her book, "Bunny Tales."

St. James has nothing good to say about Sandy Bentley. "From what I was told by the mansion staff, the twins, Sandy and Mandy, had caused Hef a lot of heartache and grief," she says.

Heartache, she says, like when Hef learned Sandy was cheating on him while still sharing his bed.

"You're not supposed to date other guys," she explains. "You know, Hef is very possessive ... When you're his girl, you're his girl."

Video: Izabella St. James on life in the mansion

But in the late summer of 1999, while still at the Playboy Mansion and long before Sandy Bentley began dating Michael Tardio, she quietly became involved with multimillionaire Mark Yagalla, a self described Wall Street whiz kid.

Yagalla had big dreams. And Sandy Bentley quickly became a part of them when he was introduced to her by another Playboy model.

"I was looking for the ultimate trophy," Yagalla tells Van Sant. "I stole her from Hugh Hefner, the ultimate heterosexual icon."

"The mild mannered guy who looks like he should be on "Wall Street Week" - you stole his girl?" asks Van Sant.

"Yes," Yagalla replies.

"And was Hef happy with that?"

"No, he was not... I am persona non grata at the Playboy Mansion."

Head over heels, Mark Yagalla began buying his Playboy Bunny spectacular, world-class jewelry - like an exact copy of the ruby and diamond necklace and earrings that Richard Gere gave Julia Roberts in the movie "Pretty Woman."

"It was her favorite movie," he says. Asked how much those jewels cost him, Yagalla replies, "A quarter of a million."

Adding insult to betrayal, Hef didn't know during an interview with CBS' "The Early Show," that Sandy was wearing Yagalla's diamonds - a $150,000 necklace and earrings set.

This was just the tip of the diamond iceberg. When Sandy wanted bling, Yagalla couldn't say "No."

"....two Rolexes, diamond rings. There's about a million dollars right there," Yagalla points out to Van Sant as they watch video of the contents of a home safe.

"You bought a watch worth half a million dollars? Are you nuts?" asks Van Sant.

"Yes," Yagalla replies. "I just wanted to make her happy."

"And material things made her happy?"

"Very, very happy."

Yagalla even spent about $3 million buying and redecorating a house for Sandy in Las Vegas.

Asked if he was in love or crazy, Yagalla tells Van Sant, "I think both."

"Mark Yagalla showered Sandy Bentley with millions of dollars worth of gifts... furs, cars, jewelry. And it's that jewelry that becomes key to this case," says Blankstein.

Why? Because after Yagalla and Sandy broke up, she took that jewelry into her relationship with her new boyfriend, Michael Tardio - one of the two men murdered in that SUV.

"Everyday, I feel like a fool," Yagalla says. "My greed and then, you know, her greed ... resulted in the... murders of two innocent people!"