Clifton Blackwell left his victim, Mahud Villalaz, with second-degree burns after confronting him in the Wisconsin city for parking too close to a bus stop, according to court filings.
He then began to berate the 42-year-old, a US citizen born in Peru, asking him "Why did you invade my country?" and "Why don't you respect my laws?"
Mr Villalaz said he moved the vehicle following the complaint, but his assailant continued – calling him “illegal” and telling him to “go back”. Mr Villalaz then called Mr Blackwell racist and said that native Americans had called the country home for the longest time, stating "everyone come from somewhere first" .
It was then Mr Villalaz said his attacker threw acid across his face, in an attack captured on CCTV cameras from a nearby restaurant. Officers said the acid was stored in a metal flask Mr Blackwell had pulled from a satchel bag.
He has since been charged with first-degree reckless injury, which carries a maximum penalty of 15 years in prison and 10 years of extended supervision. The addition of the hate crime charge could add an additional five years to his jail time.
Investigators who searched Mr Blackwell's home found four bottles of sulphuric acid, muriatic acid, and two bottles of Kleen-Out drain unclogger that was 100 per cent lye, according to the search warrant.
He remains in Milwaukee County Jail on a conditional $20,000 bail.
As he appeared in court for the first time to hear his charges, Mr Villalaz spoke briefly to reporters – saying he was thankful for “the people who have worried about me”.
He added he was pleased with the charges and had been called by Democratic Senator Tammy Baldwin, who said she was "very sad" about what had happened while offering to help however she could.
"It's been nice to know that there are many people here that worry about other people” he said. “Not only Latinos... people of all colours. We must unite,"
The charge marks a rare instance of hate crime legislation being used in the Milwaukee county court – deployed only six times from 2007 to 2018 according to analysis by the region’s Journal Sentinel newspaper, which found just 147 cases of hate crimes being brought forward across the state.
Mr Blackwell will next appear in court on 15 November.