Crazy but this is pretty common. Usually the drivers are elderly. They hit the gas thinking its the brake and when the car starts accelerating instead of braking (like they are use to) they push harder on the pedal thinking they arent braking hard enough.
Ive seen this numerous times. Last time, an elderly lady was leaving a car wash slamming the gas pedal as she was approaching the street (thinking she was hitting the brake)...ran across 5 lanes of traffic, into a parking lot, across two rows of shrubs and ending into an apartment building and someones kitchen. Didn't take her foot off the gas the entire time.
Again luckily no one was hurt.