One detail that stood out from the beginning — as the story went viral and as the bicyclist turned assailant Anthony Brennan got arrested — was how much larger he was than the three young people he attacked.

In particular, Sarah and Callan Daniel stand a little more than 5 feet tall each. On that day last June, the 19-year-old sisters had been hanging fliers against police brutality along a bike trail in Bethesda.

Brennan, listed in court records as 6 feet 2 inches tall and weighing 205 pounds, rode by, saw the fliers and didn’t like their content. He turned around. He confronted Callan Daniel, grabbing her wrists and pulling at fliers in her hand.

“To my horror,” Callan said in court Tuesday, “you charged at my sister. You loomed over her, ripping things from her hands, tearing at her wrists, screaming as you backed her against a fence. . . . Though our faces were blurred in the videos, my friends recognized me by my screams.”

It was her and her sister’s first public comments about the encounter. Moments later, Brennan, 61, was sentenced to three years of probation for three counts of misdemeanor assault, ending a case that touched on today’s contentious political culture, a bottled-up temper and what Montgomery County Circuit Judge Eric M. Johnson labeled genuine remorse by the defendant. He had pleaded guilty in the case.

“The court finds his apology to be sincere. The court did not find that he made excuses for his conduct, and that’s important,” Johnson said, speaking at the end of an hour-long hearing that revealed new details about what happened.

Brennan’s assault convictions rested on him grabbing Callan and Sarah Daniel, and in the case of Sarah, yanking a roll of blue masking tape from her forearm so forcefully he left a bruise, according to court testimony. Brennan also pushed their friend, Isaac Hillman, 18 at the time, causing a minor cut to his leg, prosecutors said.

The case, having erupted just outside the nation’s capital, drew significant interest amid a summer of protests and unrest. That it took place on a popular biking spot that cut through an affluent suburb only heightened the media’s interest.

At the time, Brennan saw the fliers as inflammatory, according to his attorneys.

“Killer cops will not go free,” one of them read.

“A man was lynched by the police. What are you doing about it?” another read.

In court Tuesday, Brennan’s attorney David Moyse said his client also was governed then by broader problems connected with years of alcohol and marijuana abuse. And income from his sales job had disappeared during the pandemic.

“I was in a bad, fragile state of mind at the time of the incident,” Brennan said. “I should have better controlled my emotions and behavior.”

His aunt Ginny Daly, who spoke during the hearing, put it a different way: “He exploded. He went off the rails. He snapped.”

As a child, according to Daly, Brennan formed a lifelong habit of keeping emotions bottled up inside and tried to protect himself with an artificial coating.

“As we all know, at some point, a shell around you is going to crack,” she added.

On June 1, that occurred after Brennan left his home in Kensington and pedaled to the Capital Crescent Trail, which has a biking stretch from Bethesda to the Georgetown area of Washington. Little was said directly about his politics on Tuesday, though Moyse hinted at them.

“He was consumed by listening to different outlets of media,” the attorney said, adding that Brennan was upset by recent damage by rioters to historic St. John’s Church in Washington. “He was riding around and seeing so much unrest. . . . These fliers said, ‘Killer cops cannot go unpunished.’ ”

When Brennan first approached the three friends, Hillman thought he was simply curious about what the fliers said. Instead, Brennan “forcefully ripped” the fliers from the young man’s hands, according to court records. He demanded that the three take down the fliers they had hung.

Then Brennan went after Callan Daniel.

“He was instantly intimidating,” she said in an interview after the hearing. “There was a lot going on in the power dynamics, whether it was size, gender or the age difference.”

Unable to pull the fliers from her hands, Brennan turned to Sarah Daniel. He backed her into the fence, grabbed the tape and headed back to his bike. Then he pushed it toward Hillman, sending him to the ground. Brennan climbed back on the bike and circled the three.

“Deviants,” he yelled, according to court records, before trying to punch Hillman and missing.

“They were scared,” prosecutor George Simms said Tuesday. “They did not know what more the defendant would do to them.”

But Brennan left, riding off down the path.

Hillman later posted video of the encounter, and it quickly took off. The Maryland-National Capital Park Police, responsible for the trail, posted stills from the video, asking for help — inadvertently setting off a frenzy among Twitter detectives. They compared the police image with photos they found online to try to determine the identity of the mysterious cyclist, his face partially concealed by mirrored sunglasses and an orange helmet. Two innocent people were publicly named as the attacker — a marketing executive and a retired police captain.

Investigators soon closed in on Brennan, in part after getting tips from neighbors who saw the images released by the police.

They searched his home, with Brennan’s permission, finding biking gear and clothes that matched the video: “Sunglasses, bike helmet, cycling shoes, blue bandanna, water bottle, shorts,” Detective Crystal Lopez later wrote in an affidavit filed in court.

Brennan turned himself in on June 5 and posted bond. Abrasive online commentary abounded.

Brennan also received death threats — online and through physical mail, according to Moyse. A small protest march that started in central Kensington, Moyse added, ended up outside Brennan’s home.

He moved out, checking into a residential treatment program for 28 days. Then, he moved into a group home for those with addictions. On Christmas Eve, Moyse said, Brennan moved back home with his wife. He has gotten sober. He attends support meetings at least several times a week.

“To me it seemed as if God was sending me a message to change,” Brennan said in court Tuesday, recalling the day of the attacks. “I got that message. I’m doing all the things I can to make changes. I cannot defend my actions that day. I can only apologize, try to change and move on. We can all agree my behavior was wrong. Again, I’m very, very sorry for what I’ve done to these young people.”

The Daniel sisters, both sophomores in college, said Tuesday that they tried to cling to their privacy as the case caught national attention.

“I really felt for them,” Sarah Daniel said of the two who were misidentified. “I can only imaging how stressful it was for them.”

As for Brennan, Callan Daniel said they were oddly in it together as the story exploded.

“It was a very strange thing to see it go viral,” she said. “He had it a lot more negatively, obviously. There is a sense of feeling bad for him as a person, on a human-to-human level.”