That was most likely a broken disconnector....or he did a poor job of stoning the sear and/or mating it to the disconnector. Saw it happen several times with USGI 1911 45 Pistols.Ive seen a guy with a broken sear in his 1911 go full auto at the range. It was unintended of course and I think he had to check his drawers after.
That foregrip is definitely illegal on a pistol in California.
What a freedom to be able to walk into a gunshop and order or have made a full auto. If you can afford it.