Police say the two girls, ages 8- and 12-years old, were playing in a yard in the 25700 block of 16th Avenue South at about 7:15 p.m. when they were hit, according to Sgt. Doug Jenkins with the Des Moines Police Department.
Witnesses told police a man in a 2012 Nissan Rogue was speeding down 16th Avenue when he crashed into a parked car and then drove onto the yard, hitting the girls.
"We've got two kids that were hit by a car and people just can't comprehend how someone could leave the scene of an accident like that," Jenkins said.
A neighbor was outside at the time and saw the whole thing unfold.
"There were two little girls walking and the guy just hit her," one witness said. "She flew. She flew and hit herself on the back of the head."
The driver then sped away, but not before witnesses got his license plate number. They called 911 and reported the crash, and police soon traced the car to a Federal Way house.
When they arrived at the home, officers found the Nissan and arrested the alleged driver. Police do not yet know if drugs or alcohol played a role in the crash.
The girls were taken to a local hospital with non life-threatening injuries, according to Jenkins.