Mehdi, 24, who is also from Tehran, echoed her assessment of the scale of the protests and violence.
“I had never seen anything even close to this level of turnout and such killings and violence by the security forces,” he said.
“Despite the killings on Thursday [8 January] and threats of more killings on Friday, people came out, because many of them could no longer endure it and had nothing left to lose,” he added.
Mehdi described witnessing multiple killings of protesters at close range by security forces.
“I saw a young man killed right in front of my eyes with two live rounds,” he said.
“Motorcyclists shot a young man in the face with a shotgun. He fell on the spot and never got back up.”
The US-based Human Rights Activists News Agency (Hrana) says it has so far confirmed the killing of at least 6,159 people since the unrest began, including 5,804 protesters, 92 children and 214 people affiliated with the government. It is also investigating 17,000 more reported deaths.
Another group, Norway-based Iran Human Rights (IHR), has warned that the final toll could exceed 25,000.
Iranian authorities said last week that more than 3,100 people had been killed, but that the majority were security personnel or bystanders attacked by “rioters”.
Most international news organisations, including the BBC, are barred from reporting inside Iran. But videos showing security forces firing live ammunition at crowds have been verified by the BBC.