The American Civil Liberties Union (ACLU) of Arizona on Wednesday called for an independent probe into potential excessive use of force against protesters outside of President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE’s Tuesday rally in Phoenix.

“The police failed to protect the First Amendment rights of protesters. Shortly after Donald Trump finished attacking the First Amendment rights of the press inside of the Phoenix Convention Center, Phoenix police began attacking the First Amendment rights of protesters outside,” the ACLU of Arizona’s executive director, Alessandra Soler, said in a statement.

“They used harmful chemical agents against a peaceful crowd, which turned a nonviolent gathering into one where many, many people were harmed. Law enforcement’s decision to swiftly and brutally end hours of civil protest could profoundly chill the freedoms of speech and assembly in Phoenix for years to come.”

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The call from the organization comes after police used pepper balls on Tuesday as protesters took to the streets of Phoenix to demonstrate against Trump’s rally.

The ACLU said it has “received many complaints” from individuals who were “taken by surprise when the police bombarded them with chemical irritants, with no warning.”

“Who in the future would want to take the risk to protest in Phoenix when it is clear that the city’s police department will take physical action against them without cause or notice?” Soler continued in her statement. “The health risks associated with deploying so-called ‘nonlethal’ weapons cannot be understated. Tear gas and pepper spray can have devastating health effects.”

Trump has mostly recently caught the ire of protesters around the country over his remarks following the attack in Charlottesville, Va., earlier this month that left one person dead at a white nationalist rally when a vehicle rammed a crowd of counterprotesters. The president has specifically faced criticism for statements in which he said “many sides” and "both sides” were to blame for the violence.