Putnam County, Florida, deputies are trying to figure out how a toddler got his hands on a .45 caliber handgun before he accidentally shot his mother as she drove down a highway Tuesday afternoon.

Deputies found a truck and horse trailer in the middle of travel lanes on Highway 20 near Rowland Avenue just after 3 p.m.

When they approached the truck they found 31-year-old Jamie Gilt in the front seat with a bullet wound.

Police said the 4-year-old shot his mother through the back of her seat as she was driving.

She was taken to UF Health and is in stable condition, according to deputies.

The 4-year-old is now with family members.

Deputies said she was on her way to pick up a horse from family who lived nearby.

The Department of Children and Families has been notified, according to deputies.