By early afternoon, three friends had hung 50 fliers in and around a popular bike trail that cuts through Bethesda.

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

“Killer cops will not go free,” read another.

What happened next, according to a newly filed police affidavit, led to a harsh, video-recorded encounter that would be viewed on cellphones around the world. It sent local investigators looking for an enraged bicyclist last seen wearing an orange helmet and silver sunglasses — a search aided by tips from his neighbors and facial recognition software.

On Friday, investigators in Montgomery County arrested Anthony Bernard Brennan, 60, on three counts of second-degree, misdemeanor assault.

According to the affidavit, filed in Montgomery District Court, Brennan attacked all three flier hangers he came across: a 19-year-old woman, with whom he is accused of getting into a tug-of-war over the fliers; another 19-year-old woman, whose right arm he reportedly bruised after yanking a roll of blue painter’s tape from it; and an 18-year-old whom investigators say Brennan shoved with his bike and tried to punch.

The affidavit also reveals that in the hours before his arrest, Brennan allowed investigators to search his home, where they found cycling garb that matched what he was wearing in the video, and that Brennan also took them to his bike, parked about two miles away behind an office building. The items were seized as evidence.

Brennan posted a $5,000 bond early Saturday and was released from the Montgomery County Detention Center. In subsequent written statements to The Washington Post, two of his adult children stressed that what he did was inexcusable, and he feels deep sorrow over it.

“My dad is genuinely sick with remorse for his actions and the pain and fear he has caused,” wrote his son, JP Brennan. “He has his struggles that he has been working through for many years that sometimes overshadow the man he is, but trust me, the love is always there. He, like all of us, has work to do understanding racial injustices.”

His daughter, Meagan Brennan, said: “I am extremely hurt and upset for what he did. It was a very bad thing, but it does not define who he is.”

The incident Monday unfolded as mass demonstrations have filled the streets of American cities in an outcry over the killing of George Floyd, the 46-year-old black man who died in the custody of Minneapolis police. As video of what Brennan did exploded across the Internet on Thursday, people on social media began positing his identity. Two men, including a retired police officer, were publicly named by Twitter users as the assailant — even though authorities would later say they had nothing to do with the incident.

In an interview, one of the victims, the 18-year-old who recorded the encounter, said that he has recently been working with the #signofjustice project on Instagram, distributing about 500 fliers in Bethesda and adjoining areas of Northwest Washington.

“I wanted to inspire people to take action and show them what they can do,” he said. The teen discussed what happened on the condition of anonymity because of fears for his safety.

By about 12:45 p.m. Monday, Brennan had boarded his bike, was in the area of the Capital Crescent Trail, and had noticed the lynching flier, according to his attorneys, Andrew Jezic and David Moyse.

On the trail, Brennan “rode slowly by” the two 19-year-old women, who were putting up fliers with the painter’s tape, according the police affidavit, signed by Detective Crystal Lopez of the Montgomery County Park Police.

“He was heard saying, ‘That’s them there,’ while holding a phone up like he was recording them,” Lopez wrote.

Brennan then circled back toward the group, dismounted and asked the 18-year-old whether he could see the fliers. “He said it in a friendly way,” the teen recalled. “I thought he was intrigued.”

Brennan instead “forcefully ripped” the fliers from the young man’s hands, according to court records.

“He then goes over to [one of the 19-year-olds] and grabs her forearm with one hand and then grabs the fliers with his other hand,” Lopez wrote in the affidavit. “They then struggle for a moment, but she was able to get away while keeping her fliers.”

Brennan turned to the other young woman, approaching her as she got trapped between him and a fence behind her, police alleged. He forcefully removed the roll of tape from her forearm, causing scratches and bruises, the affidavit states. He returned to his bike but didn’t immediately get on it — instead walking it toward the 18-year-old old and using it to push the young man to the ground, police alleged. A short time later, according to the affidavit, he tried to punch the teen but missed him. Brennan accused the three of causing riots, called them “deviants” and rode off down the trail.

The next day, the Park Police released photos of the alleged attacker. The 18-year-old posted his video on Reddit. Together, the images prompted citizens to send in hundreds of possible leads.

“Several tips provided the identity of the cyclist as Anthony Bernard Brennan III,” Lopez wrote. “Tipsters requested to remain anonymous but provided details of the suspect to include they knew him personally for more than 15 years and several were neighbors of the suspect and knew he regularly rides a bicycle.”

Investigators obtained Brennan’s MVA photo and enlisted recognition software, which “provided him as a match,” Lopez wrote.

By 8:10 a.m. Friday, an undercover officer had set up surveillance near Brennan’s home in Kensington. When he saw him leave in a white Acura SUV driven by his son, the officer trailed the Acura and watched it roll through a stop sign and eventually pull into the parking lot of a church.

“He’d gone there to seek spiritual guidance about what he had done,” Jezic said.

Another officer arrived. Brennan was asked to walk outside, where an officer asked him whether he knew why the officers were there.

Brennan initially said he didn’t know, then said he loved the police and then gave the officers Jezic’s name. Less than two hours later, Jezic said, he called the detective, Lopez — initiating the process by which investigators came to search Brennan’s home.

They found gear and clothes that matched the video: “Sunglasses, bike helmet, cycling shoes, blue bandana, water bottle, shorts,” Lopez later wrote.

“Brennan also led officers to a black bookbag in his basement office,” Lopez wrote, “that contained the fliers and tape that were taken from the victims.”

Investigators left the scene, began drawing up their paperwork and stayed in touch with Brennan’s attorneys. About 8 p.m., the attorneys said, Brennan went to the Montgomery jail to turn himself in.

Dana Hedgpeth and Alice Crites contributed to this report.