Manson Echo in Philly Teen Murder Case

June 25 -- Before the night he was beaten to death, all seemed to be going well for 16-year-old Jason Sweeney. He had a new girlfriend, and he was excited about it.

"The night before they killed him, he and I had sat there talking, and he said, 'Mom, I'm dating this girl, and I've been dating her for a couple of weeks, and she's really nice,' " Dawn Sweeney, Jason's mother, told ABCNEWS' Good Morning America. "I think you'll really like her."

But his mother never met 15-year-old Justina Morley, who police say was the teenage temptress involved in the slaying of her son.

On the night of May 30, Morley lured Jason Sweeney to a wooded area called "the Trails" near the Delaware River in Philadelphia, promising to have sex with him, police said.

But once there, Sweeney was beaten to death, struck almost a dozen times with a hammer, a hatchet and a rock, police said. The killers broke all but one bone in Sweeney's face.

Acting on a tip, police arrested Morley and two brothers, Dominic and Nicholas Coia, ages 18 and 16, respectively, in the beating death. Also arrested in the beating was 16-year-old Edward Batzig Jr., Sweeney's best friend. All four are charged with first-degree murder.

‘Helter Skelter,’ Part 2?

The teens are accused of plotting the attack on their friend for at least a week. Police say that prior to the slaying, they listened to the Beatles' song "Helter Skelter" 42 times to pump themselves up for the violent frenzy that followed.

The mass murderer Charles Manson listened to the same song before he and his followers launched a killing spree in the summer of 1969.

The four teens shared a group hug after killing Sweeney, according to transcripts of testimony in a court hearing. They are accused of stealing and splitting the victim's $500 paycheck and spending it on drugs.

"The brutality of this case is really beyond the spoken word," said Philadelphia Assistant District Attorney Judy Conroy. "The injuries, and the extent of the injuries, and the amount of force necessary to inflict those injuries, is unspeakable."