A vehicle slammed into a crowd of people, killing a 32-year-old woman, police said.
Police said the helicopter was assisting law enforcement officers monitor the rally in Charlottesville.
Earlier Saturday, the president and other lawmakers decried the events in Charlottesville, where demonstrators hurled bottles, punched and kicked one another, and shouted slurs and obscenities.
It took him a while, but after a couple of formulaic, tepid tweets about the violent white supremacist rally in Charlottesville, Virginia, which continued to roil throughout Saturday morning and afternoon, Donald Trump finally stood at a podium to speak out against hatred.
Charlottesville Mayor Mike Signer said on Twitter that at least one person had been fatally injured from the vehicle attack. Please all-go home to your families.
The president said "our country is doing well in so many ways", citing "record employment" and the arrival of new companies, among other things.
Ed Gllespie, the the Republican gubernatorial nominee in Virginia, said in a statement "having the right to spew vile hate does not make it right".
Presaging Saturday's violence was another far-right rally Friday night at the campus of the University of Virginia, which included physical encountersbetween far-right protesters carrying torches and anti-racist counter-protesters. In the same speech, he said that the kind of violence seen in Charlottesville was an ongoing issue in America, and predated his administration.
In prepared remarks from his golf club in Bedminster, New Jersey, where he has been on a working vacation, Trump made the following statement: "We condemn in the strongest possible terms this egregious display of hatred, bigotry and violence on many sides, on many sides".
The clashes highlight how the white supremacist movement has resurfaced under the "alt-right" banner after years in the shadows of mainstream American politics.
Members of a self-described militia, dressed in camouflage and armed with long guns, said they meant to keep the peace between opposing protesters.
The Southern Poverty Law Center describes the rally as "the largest hate-gathering of its kind in decades".
But at no point did Trump mention white supremacists, white nationalists or groups such as the Ku Klux Klan and neo-Nazis, whose participation in the event and inflammatory rhetoric precipitated numerous violent skirmishes before the fatal auto collision.
"This is about an anti-white climate within the Western world and the need for white people to have advocacy like other groups do", he said in an interview.
Charlottesville, nestled in the foothills of the Blue Ridge Mountains, is a liberal-leaning city that's home to the flagship University of Virginia and Monticello, the home of Thomas Jefferson. They were at a park protesting the removal of a Confederate statue. They're now called Emancipation Park and Justice Park, respectively.