What a horrific tragedy.
My theory, the man was driving down the street, and it didn't occur to him that the market was there, he just drove normally and then, when he saw the people/market, it hit him but it was too late, he panicked and got confused, hit the gas pedal and it just happened. When people get to be in their 80's, their minds don't react as quickly as a younger person would....it's just a terrible accident. I think people were enraged and when you are enraged, you don't think before you do something, that's why they wanted to beat the old man up.