WESTMINSTER, Colo. -- Police are looking for a hit-and-run driver who struck a go-cart, killing an 8-year-old boy and injuring his 10-year-old brother.

The crash happened at 96th Avenue and Pierce Street at about 6:30 p.m. Saturday. The boys were identified as 8-year-old Quinton Von Duyke and 10-year-old Kaeden Von Duyke.

Kaeden was driving the go-cart in the street with Quinton sitting in the passenger side when the cart was hit from behind, police said.

Kaeden was rushed to The Children's Hospital in Denver, where he was treated for his injuries and released Sunday. Quinton died from his injuries at the scene.

The boys were two of six children in the family who were staying with their grandparents while their parents were away on vacation, according to police.

Neither child was wearing a helmet at the time of the collision.

Police asked for the public's help in locating the driver of the car that left the scene. No description of the car involved has been released. However, police said the car may have front-end damage and possibly red or yellow paint transfer from the go-cart.

Police said the driver fled the scene without checking on the boys or calling for help.

"His life was cut short by a coward," said the boys' cousin Pam Anderson as she read a written statement from Quinton's mother. "The grief we feel cannot be put into words."

"He's a beautiful boy. As the mother said, it was a coward that left them -- two young boys on the roadside by themselves. Nothing but a coward," said the boys' great aunt Norma Anderson.

Officers said it is not legal to ride go-carts on city streets. It is only legal to ride them on private property or in designated off-road areas.

"This is an unfortunate accident. We don't want to blame them. We don't want to blame the person that hit them," said Stephanie Topkoff, spokeswoman for the Westminster Police Department. "We just want to find out exactly what happened."