Prosecutors filed involuntary manslaughter charges on Friday against the parents of the Michigan teenager who authorities say fatally shot four classmates at his school earlier this week.

James and Jennifer Crumbley each face four manslaughter counts, three days after police say their 15-year-old son, Ethan, opened fire at Oxford High School, about 60km north of Detroit, killing four students and wounding seven others.

James Crumbley purchased the handgun used in the attack four days prior, authorities have said. Parents are rarely charged in connection with children’s school shootings. Unlike some states, Michigan does not legally require gun owners to keep their firearms secured from children. The attack was the deadliest school shooting this year, according to Education Week, and marks the latest in a decades-long string of mass shootings at US schools.