Matthew Bisi was walking by when the 3-foot blade "came shooting down the sidewalk."
"I was on the right side of the sidewalk, suddenly everyone started yelling 'Get down! Move!'" he said. "It was just like crazy chaos. People screaming, all the construction workers."
"I just turned, kinda ducked, put my head down," he said. "Thing came flying right by my head, missed me by that much. You could hear it coming and it went right by me," he said.
Another witness, Sean Kuilan, also recalled the sound of the blade.
"I hear the blade and see the blade literally coming off the machine," he said. "It was huge. It looked like it was from a horror flick. I couldn't believe it."
It traveled about 100 feet before hitting a tree and then sliced into a woman "straight on," according to Bisi.
"It took her right down, gashes on the side of the thigh," he said. "The force of that coming in was pretty hard."
Read more, and watch surveillance video of the incident HERE