JACKSONVILLE, Fla. -

A 12-year-old girl is in critical condition after falling off a horse Sunday, according to the Jacksonville Sheriff's Office.

It happened around 6 p.m. on Nathan Hale Road, near the Jacksonville Equestrian Center.

JSO said the girl was with family and friends when she climbed onto the horse and it took off unexpectedly, throwing her to the ground. Officers said the girl hit her head on a tree.  They said the horse was not wearing a saddle.

The girl was taken to UF Health Jacksonville with life-threatening injuries. Her identity was not released.