SALEM, Ore. (KOIN) — An 87-year-old grandmother was forced to drive for nearly 12 hours after her grandson held a knife to his own throat and smoked meth, investigators said.

Robert White’s family had been trying to help him deal with his meth addiction and put him in a hotel room for a few days, the Marion County Sheriff’s Office said. His grandmother came to get him Saturday.

The 22-year-old got into the back of her car and put a knife to his throat and told her to drive. Authorities said he smoked meth and rambled about being followed for 9 months.

Around 8 a.m. Sunday, White called 911. GPS technology helped deputies find them, and deputies stopped the car on State Street near Lancaster Drive in Salem.

The grandmother was not hurt, though she was tired, authorities said.

White faces charges of 2nd-degree kidnapping, meth possession, menacing, 1st-degree criminal mischief and violating the protective order around his grandmother.