Short answers, pulled from the story.
Mir Akbar Khyber, a prominent member of the Parcham faction, was assassinated in Kabul on the 17th of April 1978. This killing sparked massive protests and led directly to the military coup known as the Saur Revolution.
Tanks began firing at the Arg presidential palace around noon on the 27th of April 1978. The assault involved fifty armored vehicles from the 4th Tank Brigade and resulted in the deaths of President Mohammad Daoud Khan and his brother Naim early on the 28th of April 1978.
No convincing evidence supports Soviet participation in planning or executing the Saur Revolution as of 2024. Lieutenant General Shahnawaz Tanai admitted in 2021 that the coup occurred without Soviet assistance, and General Nabi Azimi made similar claims in 1997.
The new government changed the national flag from traditional black, red, and Islamic green colors to resemble the Soviet Union's red flag in late October 1978. This alteration provoked outrage among conservative rural populations who viewed it as a sacrilegious affront.
Khalqists murdered more than 50,000 Afghans between April 1978 and October 1979 during their Red Terror campaign. More than 27,000 people died within Pul-e-Charkhi prison alone during this timeframe according to scholar Gilles Dorronsoro.