Meigan and her 16-year-old sister had recently walked out of Pushkinskaya metro station when they were approached by police in riot gear and "dragged" into the back of a police van, Meigan said.
The police -- seemingly irked when a person from a radio station tied to Svoboda, a Ukrainian nationalist party -- approached the women, but they didn't have a chance to talk, Meigan said.
The pair were led into an empty police van and Meigan did what more and more people, from Minnesota to Moscow, are doing in their interactions with police: She hit record.
Soon, the police van began to fill up with protesters, mostly teenagers.
Among them was Ivan Avdeev, who was bleeding from his face and hands.
Avdeev had been holding a sign that read, "Pitiful, thief, stiff."
Sasha Nosan-Nikolskaya, 16, who was put into the same police truck, said detainees gathered napkins and helped clean Avdeev.
Nosan-Nikolskaya, who, like Meigan, was posting on social media while she was detained, took a photo of Avdeev holding a napkin with blood on it.
Later, a far more striking photo of the 16-year-old would emerge and appear in media outlets around the world: the moment the boy was tackled by police and pinned to the ground.
Despite their arrests, the protesters' spirits remained high. "We've all been detained," one person is heard saying in a video shot by Meigan, as another person responds, "For telling the truth."
"Right. For telling the truth. As the saying goes, 'the truth hurts,'" a detainee says.
The state-run Tass news agency said 136 adolescents were detained.
"According to Russian media, 70% of people at Monday's protest were in their teens or early 20s," said Jill Dougherty, a Russia expert and former CNN Moscow bureau chief. Those numbers were also true of this particular police van. Two of the people detained said those in the van ranged in age from 14 to 30 and there was one person in their late 40s.
"All the young people want to see President Navalny. And the old people want Putin. That's how we live," Meigan said on Tuesday. "We want there to be no corruption and there to be respect from the authorities."
But others in the police vehicle weren't as wholehearted in their support for Russian opposition leader Alexey Navalny, who was also arrested on Monday and sentenced to 30 days in prison
after being found guilty of calling repeatedly for unlawful protests.
"I'm more against corruption than in support of Navally," Nosan-Nikolskayan said. "And the rally was against corruption, and not just in favor of Navalny."
Likewise, Avdeev, who spoke to CNN on Tuesday after leaving a hospital, where doctors examined his hands and chin, said he wanted to see investigations into corruption in the country but said he respected President Vladimir Putin as head of state and said he would be unlikely to vote for Navalny. "For me he is not the one who can manage Russia."
The detainees were kept in the van for about an hour before being moved to Khamovniki police station.
There they were put in a room and called to speak to a police officer one by one.
Meigan was charged under laws pertaining to organizing and partaking in rallies and demonstrations. Her younger sister, a minor, was not charged.
Most of those detained in the van were released by 8 p.m., they said. None was deterred from protesting again.
"We will protest further. We are not afraid," Meigan said.