The police in Milwaukee on Monday were investigating an attack on a Hispanic man as a possible hate crime after the victim, who was severely burned on his face and neck, reported that his attacker threw acid on him and told him to “go back to your country.”

The victim, Mahud Villalaz, 42, was assaulted outside a Mexican restaurant in the Lincoln Village neighborhood of Milwaukee on Friday. He described being attacked by a white man who hurled racist insults at him and accused him of being an “ illegal” before splashing acid on him.

The police said they had arrested a 61-year-old white man in connection with the attack, but as of Monday night they had not announced any charges nor released the suspect’s identity.

Mr. Villalaz, an American citizen who came to the United States from Peru 19 years ago, said the episode began when he parked near the taqueria and was confronted by the man about how close his pickup truck was to a bus stop. Mr. Villalaz returned to his vehicle and moved it about a block away. As he walked toward the restaurant again, he said, the man said, “You came here to invade.”