The Menendez Brothers: Why Did Lyle & Erik Slay Their Mom, Dad (FPD CASE VAULT)

Beverly Hills brothers Lyle and Erik Menendez were just 21 and 18 respectively when they gunned down their multi-millionaire businessman father Jose, 45, and their mother Kitty, 48, in the blood-spattered den of the family mansion.

The trial caused a national sensation when it was broadcast in 1993 on the then-new cable network Court TV.

The heinous crime came to light on Aug. 20, 1989, when Lyle called 911, frantically telling the operator: "Somebody killed my parents!"

Their father was repeatedly shot at point-blank range in the back of the head. Kitty was blasted to a pulp as she tried to flee and was completely unrecognizable. She'd been shot in the leg, arm, chest and face.

Cops at the grisly scene noted the couple was gunned down by 15 shotgun blasts.

At first, the boys appeared to have an airtight alibi, but they raised suspicion when they almost immediately began running through their father's fortune, spending nearly $1 million on the high life in mere months.

Never miss a story — sign up for the Front Page Detectives newsletter. Be on the scene the moment news breaks.

The case broke wide open in March 1990, after Erik confessed to their shrink, who told cops after being threatened by Lyle. But it wouldn't be easy to convict the deadly pair.

The brothers' emotional testimony - weaving a tale of a lifetime of physical and sexual abuse - ended in a mistrial. The brothers were convicted after a second trial in 1996.

Lyle, 45, and Erik, 42, were sentenced to life in prison without the possibility of parole. Both got married behind bars.