First: moderate cleric Hussein-Ali Montazeri, a leader of the 1979 revolution and then a critic of the Supreme Leader and an advocate for democracy and equal rights, died on the 19th. The state news agency derisively referred to the beloved ayatollah as "clerical figure of the rioters." His funeral on the 21st became a protest of the regime. Ahmadinejad opponent Mir-Hossein Mousavi was attacked twice by Ahmadinejad supporters.
The next day, Ahmadinejad removed Mousavi as head of the Arts and Culture Academy. On the 23rd, more mourners were arrested.
Then came the Shia holiday of mourning, Ashura, which commemorates the death of the prophet Muhammad's grandson Imam Hussein, a spiritual forefather of Shia Islam.
Ashura demonstrations helped bring down the Shah, so the Khamenei regime was extremely nervous going into the weekend. The Basij, Iran's volunteer militia of hardliners aligned with the Revolutionary Guard and the Supreme Leader, began clashing with protesters almost immediately. Three protesters were reported killed in Tehran early on the first day of Ashura protests. But protesters were fighting back more than in previous demonstrations, lighting police cars on fire and beating cops who attempted to charge the crowds. Some police refused orders to fire on crowds, and at least one police officer was reportedly spotted wearing opposition green.
Killing for any reason is forbidden on Ashura. So in addition to ten dead protesters, it is absolutely insane that Khamenei then assassinated Moussavi's nephew. Ali Moussavi was run over by a car and then shot in the street. Government officials confiscated his body to prevent a funeral.
Hundreds of people have been arrested, and at the end of this, dozens could be confirmed killed. Killing Moussavi's nephew on Ashura was probably one of the dumbest decisions the regime could've possibly made. Protesters have largely switched from chants against Ahmadinejad to chants against Khamenei himself. There is, of yet, no "revolutionary alternative" to the Supreme Leader, and he controls the military and the security forces, but basically he is fucked in the long term, and a lot of Iranian dissidents are about to be locked up and killed.