When an SUV suddenly began rolling, driverless, toward a busy highway, one man didn't hesitate. He used his own car to safely block it, protecting a mother and her child from what could have been a serious collision.

Witnesses said there was no hesitation and no fanfare, just someone who saw a few seconds to act and used every one of them well.

Moments like this rarely come with warning or rehearsal. They come down to a person deciding, in an instant, to put themselves between danger and a stranger.

The mother and child were unharmed. The man who intervened told local reporters that he thinks anyone would have done the same, though not everyone does.