When Farid's friend called crying for help on Sunday, he jumped on his bike and quickly rode to Tehran's Sharif University.
"Please come save us. We are stuck here. They are shooting at us," his friend said.
Scenes of violence and "savagery" met him when he arrived at the campus of the elite university, he said, where hundreds of students had been trapped in the parking lot by Iran's Revolutionary Guard Corps, according to videos CNN verified from social media.
"They had guns, they had paintball guns, they had batons," said Farid, whose name has been changed for his safety.
"They were using gases... [that are] banned internationally... it was a war zone... there was blood everywhere."
In one video posted to social media from the scene, police can be seen detaining people and carrying them on motorbikes. In another, loud bangs are heard.
It was the first day of school, but many students had refused to join class. Instead, they were protesting against the regime, in a nationwide movement triggered by the death of Mahsa Amini, a 22-year-old who passed away last month in a hospital after being apprehended by Iran's morality police and sent to a "re-education center" for not abiding by the state's hijab laws.
For more than two weeks, protests have taken place in more than 45 cities across Iran, including the capital, with dozens of people reportedly killed in clashes with security forces.
CNN cannot independently verify claims of arrests or detentions as a precise number of protesters arrested or detained is impossible for those outside Iran's government to confirm. Numbers vary depending on whether they come from opposition groups, international rights organizations, or local journalists. State media outlet the Islamic Republic of Iran Broadcasting (IRIB) reported that at least 41 people have died in Iran in recent protests. According to Amnesty International, the crackdown has killed at least 52 people and injured hundreds more.