A YouTube video captured the fireworks accident in Simi Valley, Calif., that reportedly left at least 28 people injured, four of them seriously.
According to ABC News, the "unintended" detonation ended up shooting fireworks into a crowd during the Fourth of July celebration.
YouTube user Tim Pietrolungo captured the entire incident from a high vantage point. The video clearly shows some of the fireworks shooting horizontally and exploding at ground level.
A police investigation is ongoing. "We're still in the process of sorting out exactly what happened and treating the injured and evacuating them to area hospitals," said John Parks, the watch commander at the Simi Valley police department.