Simplify the following text for a Grade 13 native English-speaking person.
Original: Miroslav FilipoviÄ was a Franciscan friar ( from the PetriÄ evac monastery ) who allegedly joined the UstaÅ a army on 7 February 1942 in a brutal massacre of 2730 Serbs of the nearby villages , including 500 children .
Simplified: Miroslav FilipoviÄ was a Franciscan friar ( from the PetriÄ evac monastery ) who joined the UstaÅ a army on 7 February 1942 in a brutal massacre of 2730 Serbs of the nearby villages , including 500 children .