Teen Boy Finds Out He’s Adopted, Shoots Entire Family Dead, Tries to Poison Stepmom Who Has Peanut Allergy: Court Docs

An Alabama teen facing murder charges for the 2019 murder of his adopted parents also tried to poison his stepmother with peanut butter, according to recently-released court documents.

As CrimeOnline previously reported, Mason Sisk, who was 14 at the time, is accused of killing his family members at their Elkmont home in September 2019. Limestone County Sheriff’s Office spokesman Stephen Young identified the victims as the teen’s father and stepmother, John Sisk, 38, and Mary Sisk, 35; his half-brothers 6-year-old Kane and 6-month-old Coleson; and Aurora, his 5-year-old half-sister.

After the shooting, Sisk called the police to the residence at around 1:15 a.m., claiming he heard gunshots upstairs. When questioned by investigators, he reportedly changed his story and admitted to killing the family. He then helped officers locate the murder weapon on the side of a nearby road, police said.

News 19 reports that according to the latest court documents, Mason also “knowingly put peanut butter in his stepmother’s coffee despite her severe allergy to peanuts,” according to the district attorney. He later shot his stepmother execution-style, court documents state.

Further, he’s accused of stealing his stepmother’s rings and giving them away, and stealing his grandmother’s gun.

Mason Sisk/Police Handout

Mason Sisk’s cousin previously told WVLT that Mason learned Mary Sisk wasn’t his biological mother shortly before the murders. The cousin also revealed that the teen began acting out a year ago—in the form of vandalizing his school and burning animals alive.

Relatives who spoke with WAAY described Mary Sisk, a special education teacher, as the best thing to ever happen to the defendant. The teen reportedly babysat his three younger siblings and had a close relationship with his father.

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Court documents released in 2019 stated that John Sisk was granted emergency custody of his son in June 2011. The defendant hadn’t seen his biological mother since 2008, when he was about 3 years old. Documents stated that the biological mother died the same day the emergency order was granted.

John Sisk was scheduled to stand trial for burglary in November, according to the news station. Young confirmed the gun used in Monday’s slayings was in the Elkmont home “illegally.”

Sisk remains behind bars and will face trial in adult court. However, the death penalty will not be applied due to his age when crimes happened.

Check back for updates.

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[Featured image: John Sisk/LinkedIn; Mary Sisk/Huntsville City Schools; Kane, Coleson, and Aurora Sisk/WHNT video screengrab]