Simplify the following text for a Grade 2 native English-speaking person.
Original: On July 25 , 1958 , in Nueva Helvecia , Uruguay , Mengele remarried to Martha Mengele , the widow of his younger brother Karl . Marthe Mengele had arrived in Buenos Aires in 1956 with Karl-Heinz , her son from her first marriage .
Simplified: Mengele was known as the Angel of Death .