WASHINGTON — When Attorney General Jeff Sessions denounced the violence in Charlottesville, Va., as an “evil” act of domestic terrorism on Monday, he was in some ways an unlikely figure to emerge as one of the most prominent voices in the Trump administration on the issue.

Though he is the nation’s chief law enforcement officer, Mr. Sessions, an outspoken Alabama conservative, is viewed with mistrust by many civil-rights advocates concerned about his ambivalence over expanding protections for minorities.

But he has stepped outside that mold in aggressively responding to the deadly car attack by an apparent white nationalist sympathizer on anti-racism protesters in Charlottesville, announcing a federal civil rights investigation within hours and labeling the attack an act of domestic terrorism during a string of television appearances on Monday.

“You can be sure we will charge and advance the investigation toward the most serious charges that can be brought, because this is an unequivocally unacceptable and evil attack that cannot be accepted in America,” Mr. Sessions said on ABC’s “Good Morning America.”