Two children suffered severe injuries this evening when they were struck by a car near Pioneer Parkway and Daniel Drive in Arlington, police said.

One child, about 5, was flown to a hospital by helicopter, and another, about 12, went by ambulance.

They were with a group of kids who tried to cross in a dark section of road shortly before 8 p.m., police said. The driver stopped to help after the crash.

It was unclear where the children were headed.

“There are a couple of stores in the area,” said Tiara Ellis Richard, a police spokeswoman. “So they might have been leaving the neighborhood and walking across the street to a grocery store or a convenience store.”