- Early October 1941 - members of the resistance attack German units near Gornji Milanovac, causing enemy losses of 10 killed and 23 wounded soldiers
- 20 and 21 October 1941 - in retaliation, the German forces shoot 2,796 civilians (2,381 in Kragujevac and 415 in the surrounding villages), among whom students from the Kragujevac grammar school
- 1976 – the 21 October museum is built as part of the Sumarice memorial park
After the partisan attack on the units of the 3rd Battalion of the 749th regiment in the vicinity of Gornji Milanovac, during which the German forces suffered 10 fatalities, with 26 injured, the regiment commander, following general Böhme’s instructions, ordered retaliation against the civilian population. 422 men were executed in the villages around Kragujevac on 19 October. In the days that followed, the German forces, together with the quisling formations, would carry out mass arrests in Kragujevac itself. Students of the whole grades of local secondary schools, such as the first and the second grade of the Teachers’ College or the fifth grade of the Kragujevac Grammar School were among the arrested. All of them were placed at the local concentration camp buildings, where all male Jews from Kragujevac, around 80 of them, had been kept since 18 October. The execution by shooting took place on 21 October, at three localities in the vicinity of the city, most of them at a place known as Šumarice. As many as 2,300 civilians were executed that day.
The Ljotić’s 5th volunteer squad, under the command of Marisav Petrović arrived in Kragujevac several days before the shooting. It was one group of the 5th volunteer squad, under the leadership of Momcilo Zdravkovic, called “Izrila”, that had the assignment to collect the Roma. The following day, on the date of the execution, Ljotic’s men tried to single out those whom they considered capable of becoming the new “volunteers” from the big group of arrested Kragujevac citizens. In exchange for them they handed over other hostages to the Germans, mostly Roma, more of them than the Germans had requested. According to some estimates, roughly 200 Roma were executed.
In 1953, a memorial park was organised on the site of the executions, and the 21st October museum was built in 1976. It still represents one of the key institutions of its kind in Serbia. The memorial park comprises 10 monuments dedicated to the victims, in front of which commemorations are held every year.