MUSCATINE, Iowa (AP) – A 20-year-old Muscatine man has been found guilty of first-degree murder for the 2018 stabbing death of his grandmother on her birthday. The Muscatine Journal reports that the jury on Friday found Darian Lensgraf guilty of killing 66-year-old Diana Lensgraf on Dec. 12, 2018.

He faces a mandatory sentence of life in prison when he’s sentenced on March 6. He remains behind bars until his sentencing. Lensgraf was arrested after a convenience store clerk called 911 to report that Lensgraf was in the store holding a bloody knife. His grandmother’s body had been found only minutes earlier.