"So they chased after him, and he revved it up and slashed one of them across the arm and then he ran all the way down one of the streets.
"He cut the guy across his bicep. There was quite a bit of blood.
"Me and a few of my mates chased him to Anglesea St. He was revving it as he was running down the street and then he stopped. Around 400 metres down the road he stopped and turned and started walking towards me.
"He stopped and faced me and I managed to convince him to put them [the weapons] down."
The witness told the Herald there were "heaps of people" who witnessed the attack on Victoria St, and then a group who chased the man with the electric saw through the streets of Hamilton's CBD.
A group of bystanders helped restrain the man after he dropped the electric circular saw and a crowbar he was also holding, the witness said.
"It looked like a 12-volt battery drill, and it had like a hand guard on it. So you had to use it with two hands to get the blade fully out, but he had the blade down maybe 10 mills," the witness said of the weapon.
Police said a man, 22, had been charged with intent to cause grievous bodily harm.