A Wisconsin teenager has been charged after reportedly admitting injecting a cow tranquilizer into his stepfather’s energy drinks as a prank. Tyler Rabenhorst-Malone, 17, is reported to have said he never meant to harm his stepdad—he just thought it’d be funny. The stepdad went to a hospital in January 2018 with a droopy face and slurred speech, among other symptoms, which he believed to be as a result of stress, lack of sleep, and too many energy drinks, the New York Post reports. When it later happened again, he started to become suspicious about the drinks, and the teen’s mother noticed that a box of oxytocin mixed with rompun had vanished from their barn. The stepfather then discovered used syringes he believed Rabenhorst-Malone was using to put the sedative in his drinks, according to the complaint. Officials say the drinks and syringes tested positive for Xylazine—a drug used for tranquilizing large cattle. The teen is due in court later this month.