Beverly Hills brothers Lyle and Erik Menendez set the gold standard for greed.

On August 20, 1989, the handsome brothers — Lyle was 21 at the time, while Erik was 18 — brutally murdered their parents, Jose and Kitty Menendez, in the den of their Beverly Hills mansion. Police originally thought the killings were a mob-style hit, which is just how the brothers staged it.

And they almost got away with it, until their greed went too far.

The investigation, and two criminal trials that followed, transfixed a nation at the dawn of the tabloid TV era. Nearly three decades later, the story still fascinates. It is even the subject of a new series, "Law & Order True Crime: The Menendez Murders," premiering this fall on NBC.

Lyle and Erik planned their parents' murder meticulously. They forged the paperwork to purchase two 12-gauge shotguns. They cooked up an alibi, telling investigators they had gone to see a movie at the time of the murders. They even shot their parents in the kneecaps to make the killings look like gangland hits. Police bought it at first, investigating the business ties of Jose, a media executive.

Beverly Hills Police Detective Les Zoeller — who has since retired from the force — said he initially had "no inkling" the brothers might be involved, even though Lyle seemed unusually calm on the night of the murders.

"Lyle didn't seem upset to me at all. He was matter of fact. He wanted to get things out of the house," Zoeller told NBC's Today Show last year. "It struck me very odd."

But soon, things would start to make sense.

Not long after the murders, the brothers went on a spending spree. They bought luxury condominiums for themselves in tony Marina del Rey. Lyle bought a Rolex, a Porsche, and a restaurant in Princeton, New Jersey. Erik bought a Jeep Wrangler, hired a $50,000-a-year tennis coach in hopes of turning pro, and invested $40,000 in a rock concert with a promoter who ultimately stiffed him, according to Vanity Fair writer Dominick Dunne.

In the six months after their parents' death, the brothers spent an estimated $700,000.

"The brothers were out there spending money like it was water," Zoeller said.

In March of 1990, seven months after their parents' deaths, Lyle and Erik Menendez were arrested for murder.

Boston psychologist Karen Weisgerber, who was not involved in the Menendez case, said it should come as no surprise that the brothers had a blind spot when it came to money. She said it is a common thread among the wealthy families she specializes in.

"Money becomes a substitute for having a relationship," Weisgerber said.

The situation can be even more intense in families with self-made riches, like the Menendez family.

"There is a lot put on being able to create wealth," Weisgerber said. "They tend to measure performance and success by concrete measures."

Jose, who emigrated from Fidel Castro's Cuba when he was 15 years old, worked his way up the business ladder to become CEO of a video distribution company. At the time of his death, his fortune was estimated at $14 million.

The brothers claimed they killed their parents to escape a lifetime of abuse, including sexual abuse by Jose. The defense was enough to get the brothers a hung jury in their sensational first trial, which was telecast live on the still-new Court TV. Actually, two juries — one for each brother — deadlocked in the case.

But in the second trial, with a single jury and cameras barred, jurors rejected the abuse defense and convicted the brothers of first-degree murder and conspiracy to commit murder. They are serving life sentences in prison without the possibility of parole.

Weisgerber says beyond being a tabloid curiosity, the Menendez case offers some lessons to families when it comes to money.

"I have met parents with the best intentions who give their children money to do certain things," she said. "Is that how you're demonstrating care?"

The effect on the children can be profound, ranging from distance and separation to increased risk taking such as drug abuse.

"Whatever life lessons and moral compass that the parent can provide is lost in the shuffle," she said.

Weisgerber counsels families to have open conversation about money, wealth, and expectations.

"We always come back to communication, communication, communication," she said.

Greed, after all, is a learned behavior, and it takes hold early. In the case of the Menendez family, the result was unspeakably tragic.

"Law & Order True Crime: The Menendez Murders" premieres Tuesday, Sept 26 at 10/9c on NBC.