A 16-year-old male suspect was arrested in the slaying of famed criminal defense attorney Daniel Horowitz's (search) wife, and a newspaper reported Thursday that he clubbed her to death with a piece of crown molding while looking for marijuana-growing equipment.

Police would not identify the teenager and said they were still working to determine a motive for the beating death Saturday of Pamela Vitale (search).

"Although we have a suspect, the investigation is still going on," said sheriff's spokesman Jimmy Lee. "Much more work still needs to be done."

Vitale, 52, was slain over the weekend at the hilltop estate where the couple were building their dream home in the wealthy San Francisco suburb of Lafayette. The teenager lived down the hill on a remote canyon road. He was arrested Wednesday night.

The San Francisco Chronicle reported that an anonymous law enforcement source said police believe the teenager killed Vitale by striking her with a piece of crown molding 39 times in the head — and then carved some kind of gothic signature into her back.

The suspect had scratches on his legs and face consistent with a violent altercation when cops arrested him at a relative's house, the Chronicle reported.

The paper, citing the law enforcement source, said the motive was related to a scheme involving stolen credit card numbers to fund a marijuana-growing operation.

The source said the boy had ordered equipment for the pot operation and mistakenly thought the supplies were delivered to Horowitz and Vitale's home, the newspaper reported on its Web site.

He went there Saturday looking for the equipment and got in a fight with Vitale, striking her dozens of times in the head with a piece of molding that was left behind at the scene, according to the source.

"She fought back very hard. That was very obvious from the scene," Horowitz said Wednesday, adding that his wife had a head wound.

Police asked anyone with information in the case to call 866-846-3592.

Horowitz said he discovered his wife's body when he returned home after working on the case of Susan Polk, a woman accused of stabbing to death her therapist husband.

Vitale worked part-time for her husband's law firm and had been in the front row of the courtroom during opening statements.

Horowitz rose to national prominence as a cable news commentator during the Scott Peterson (search) murder trial. He was in seclusion Thursday with friends and family as they prepared for Vitale's funeral.

FOX News' Andrew Hard and The Associated Press contributed to this report.