It was 1972, and Joe Biden had just been elected to the U.S. Senate in Delaware when his first wife, Neilia Hunter Biden, decided to take the couple’s three children to get a Christmas tree. Neilia and young Naomi didn’t survive the trip. Sons Hunter and Beau were in the car but survived the accident.
Source: https://heavy.com/
According to Politico, the Biden vehicle was struck by a truck carrying corncobs as they journeyed to pick out a Christmas tree.