Masked federal agents grabbed a couple men off the sidewalk outside a Home Depot in Los Angeles … including one man who threw a glass object at their unmarked van, and bystanders claim he’s a U.S. citizen.

TMZ shot video of a dramatic immigration raid Monday morning … and a swarm of masked agents in blue jeans, sneakers and tactical gear detain a day laborer looking for work in a hauling truck. We’re told the day laborer’s name is Hector.

As the masked men — some wearing police vests — drive off in an unmarked van, a guy on the sidewalk watching the raid with his mother throws a glass object at the van and it shatters. The van comes to a screeching halt, and the occupants rush over to the guy and detain him … as the man’s mother begs them to stop and people scream that he’s a U.S. citizen.

Onlookers whip out their phones, and the masked agents point firearms. Interestingly, the at least one of their guns appears to be fitted with a paint pellet loader … something we haven’t seen previously during the immigration raids.

After hauling the bottle thrower into their unmarked van, one of the masked men lets loose that they are taking the guy to an ICE facility in Los Angeles.

Local cops were called to the scene, but the commotion was long gone by the time officers arrived.