UPDATE: Just before 1:00 pm Thursday, Stone Mountain Police announced they made an arrest in the hit-and-run. Details are at the bottom of the story.

STONE MOUNTAIN, GA. -- Gustavus Wilson was inside his insurance office on Main Street in Stone Mountain when he heard a loud noise. He didn't think much of it. The stretch of asphalt has a speed limit of 25 mph, but a steady stream of traffic moves through at a much faster clip.

When he looked outside moments later, he saw a woman lying in the middle of the road.

“She was motionless for a minute, so you didn’t really know what had happened. You were really hoping for the best, but it was a horrific sight to see once your realized what happened.”

What happened was a hit-and-run. Police say the 66-year-old woman was crossing the street when an older model white car hit her. And kept going.

The woman was bleeding from her head and told people who stopped to help she couldn't move her arm. First responders found additional injuries on her torso and a dislocated shoulder. She was transported to Grady Hospital where she is said to be critical but stable.

“To keep going like that, it just really a disregard for human life like that, I’ve heard that lady probably will survive, but it is just unfortunate that they kept going," Wilson said.

More than unfortunate, it's illegal.

Using cell phone video, investigators determined that it was a white Chrysler 200 that hit the woman.

By Thursday afternoon, police said the vehicle had been recovered and a suspect had been arrested. Demetric Williams, 24, is charged with leaving the scene of an accident, duty to make immediate reports of accidents and serious injury by vehicle.