Brothers ages 11 and 13 were thrown from a piece of horse-drawn farm equipment they were operating, and the younger boy was run over and killed, authorities said.

The incident occurred about 9:20 a.m. Friday on an Amish family’s farm about 9 miles southeast of Milaca, Minn., on 110th Street, the Mille Lacs County Sheriff’s Office said Monday.

The boys were thrown from the implement, a manure spreader, after it hit a rock in the field while being pulled by a team of horses, the Sheriff’s Office said.

Authorities have not released the boys’ identities.

Addressing whether the young ages of the boys operating farm equipment violated any laws, Sheriff Don Lorge said Tuesday, “There really isn’t any that I am aware of.”