Tommy Sullivan Jr. Killed His Mother With a Boy Scout Knife — What Happened to Him?

Life is full of unexplainable mysteries, from the murder of JonBenét Ramsey to the case of the “Boy in the Box.” And there are plenty more like them. Take the murder of Betty Ann Sullivan, 37, a mother of two who was stabbed to death by her son, Thomas “Tommy” Sullivan Jr., when he was just 14 years old in 1988.

The case is now at the center of the four-part MGM true crime docuseries Let the Devil In, which premiered on Aug. 31, 2025, more than 37 years later. While there’s no mystery about who committed the horrific act, the motive still leaves many people confused and even a little frightened. Some speculate that satanic practices influenced Tommy Jr.’s actions.

With Tommy Jr.’s crime back in the spotlight, the question remains: whatever happened to him? Here’s the scary truth.

Tommy Sullivan Jr. killed himself after taking his mother's life on Jan. 9, 1988. The 14-year-old reportedly got into an argument with Betty Ann over his newfound interest in satanic rituals. According to The Los Angeles Times, the argument sent him into “a rage,” and he used his Boy Scout knife to stab her multiple times.

Afterward, he carried her body to the basement of their Jefferson Township, N.J., home. He later placed several books in a circle on the floor, topped them with newspapers, and set them on fire.

Tommy Jr.’s father, Thomas Sr., and his 10-year-old brother, Brian, were awakened by the smoke alarm, and that’s when Thomas Sr. found his wife’s body.

Thankfully, he and Brian escaped before the flames consumed the house. As for Tommy Jr., he fled to a neighbor’s yard, where he slit his own throat.

It’s believed Tommy Jr. set fire to the family house to cover up the murder and potentially kill his remaining family members. But, according to the media outlet, a suicide note was retrieved from the home, signaling that Tommy Jr. had contemplated committing suicide prior to getting into an argument with his mother and subsequently killing her. It also reportedly contained “Satan-like” symbols and “cult references.”

What’s odd, and has many, especially believers in Satan and evil energy, worried, is that Tommy Jr. had only recently become engrossed in Satan-related books, about a month before the murder-suicide.

According to a Morris County Prosecutor’s Office Facebook post, in February 1988, Prosecutor Lee S. Trumbull told the Associated Pressthat “there were no apparent problems” until Tommy Jr. began reading these books.

This has led some to suggest that Satan may have influenced him to carry out these horrific acts.

Tommy Jr.’s murder-suicide case was extremely disturbing and still leaves many wondering what influenced his actions. But he wasn’t the only teen at the time believed to be involved with Satanism.

There were other cases across the country, including one from the 1960s involving Marissa, who reportedly redecorated her room to show her devotion to Satanism, and another involving a 12-year-old boy who allegedly “ripped the head off his cat and drank the blood.”