An Alabama teen charged with killing his family tried to poison his stepmother with peanut butter prior to the cold-blooded slayings, prosecutors said.

Mason Wayne Sisk, 16, allegedly put peanut butter in his stepmom’s coffee despite knowing she was severely allergic — after he discovered they weren’t biologically related, WHNT reported.

It is unclear if Mary Sisk, 35, drank the coffee or suffered an allergic reaction before her enraged stepson then allegedly gunned her down, along with his father and three siblings in September 2019.

Prosecutors revealed the disturbing accusation in court records that also indicated Sisk — who was 14 at the time of the slayings — had threatened his father, John Sisk, and had “anger control” issues regarding his three younger half-siblings.

His siblings have been identified as 6-year-old Grayson, 5-year-old Aurora and 6-month-old Colson.

Sisk is also accused of stealing two rings from his stepmom, which he later sold, WAAY reported.

Mary Sisk had reportedly worked as a special education teacher at Mountain Gap Elementary in Huntsville.

Prosecutors said Mason Sisk, who is being tried as an adult, had stolen a handgun from his grandmother’s house prior to the gruesome murders. All five victims were shot in the head, authorities said.

Sisk, of Elkmont, pleaded not guilty to the killings in April 2021, WAFF reported. He’s due back before a judge on Aug. 12.

Prosecutors have yet to release a motive in the slayings, but previously released court documents indicate Sisk has shown no remorse while awaiting trial.

“Mason does not seem bothered by the fact he’s accused of murdering his family,” his juvenile probation officer wrote in a November 2020 report. “He has not shown any sign of remorse. While in detention, he has not talked about his family at all.”