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By Kalhan Rosenblatt and The Associated Press

The mother of the young man suspected of ramming his car through a crowd of protesters during a white nationalist rally in Charlottesville, Virginia, said she thought her son was attending a Trump-related rally on Saturday.

James Alex Fields Jr., 20, of Ohio, was taken into custody shortly after he allegedly drove his car into a crowd of anti-racist protesters, killing Heather Heyer, 32, and injuring at least 19 other people.

Fields' mother, Samantha Bloom, who was watching her son's cat at the time the incident took place, learned that her son was suspected of plowing his car into protesters only when she was approached by reporters at her home in Maumee, Ohio.

"Running his car into a crowd of people? Did it hurt anybody?" she asked after learning the news, saying she hadn't been notified of her son's arrest.

A witness who filmed the car crash said he saw the vehicle build up speed before ramming the crowd. "It was very clearly intentional," Brennan Gilmore told NBC News.

After being told about the white supremacist purpose of the rally, Bloom said she was under the impression that her son was merely attending a political rally — not a nationalist march.

"I didn't know it was white supremacists. I thought it had something to do with Trump," she said. "Trump's not a supremacist."

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Bloom advised her son to take part only in peaceful demonstrations, according to the Toledo Blade.

"I told him to be careful," Bloom told the paper. "[And] if they're going to rally to make sure he's doing it peacefully."

Bloom said she doesn't talk about politics with her son.

Related: Charlottesville Faces Its Own Past After Rally Turns Deadly

"I try to stay out of his political views. We don't — I don't really get too involved," Bloom said. "Like I said, I don't really talk to him about his political views. So I don't really understand what the rally was about."

Tanner Coleman, a former classmate of Fields', posted on his blog, describing his memories of high school with Fields.

"I do not remember a single detail of any conversation, other than thinking that he occupied the 'gentle giant,' role in my mind," Coleman wrote.

Coleman also described Fields as "kind" and "shy" but said he was often isolated and alone.

Kathy Scott, who lives in Bloom's neighborhood and said she had several interactions with the mother and son, also described Fields as "shy."

"I saw him quite a bit," Scott told the Cincinnati Enquirer. "Going to the bus and using his bicycle. But he was just shy. [Bloom] was very sociable. She went to the big church down the street called Crossroads."

A federal civil rights investigation into the ramming has been launched, and Attorney General Jeff Sessions said the probe "will have the full support of the Department of Justice."

James Alex Fields Jr., second from left, holds a black shield during a white supremacist rally on Saturday, Aug. 12, 2017 in in Charlottesville, Virginia. Fields was later charged with second-degree murder and other counts after authorities say he plowed a car into a crowd of people protesting the white nationalist rally. Alan Goffinski / AP

President Donald Trump faced bipartisan criticism after suggesting "both sides" were to blame for the violence in Charlottesville.

Democrats criticized the president for failing to single out white nationalists, and several Republicans issued statements condemning white nationalism or white supremacists.

As Bloom was told about the allegations against her son, she told reporters that Fields has a black friend.

The car-ramming attack followed a march Friday night at which hundreds of white supremacists carrying tiki torches clashed with counter-protesters on the University of Virginia campus.

Marchers alternated between chanting the Nazi-linked slogan "Blood and soil!" and "You will not replace us!" among others.