"They have no business being here man," KOB-TV, Albuquerque quoted Miguel Aguirre as saying. "I told them to leave and get out."
Later, the 48-year-old man said he was just trying to protect the campus and offered an apology, Albuquerque's KRQE-TV reported.
"I apologize to the protesters," Aguirre said.
One protester, Mark Somoza, said the Occupy Wall Street-associated demonstrators were "just minding our own business" when a man threatened them with a knife.
"Luckily there was enough of us to kind of coerce him to be calm," Somoza said.
Police apprehended Aguirre across the street, using a stun gun on him after he allegedly refused to follow their orders.
He was charged with aggravated assault.
He said he was angry at the (Un)Occupy Albuquerque protesters, a faction of the national Occupy Wall Street movement.