Complex sentence: The first to be killed was Simmons son Billy and his wife Renata, who were both shot dead; he then strangled and drowned their 20-month-old son, Trae.
Split into simpler sentences: The first to be killed was Simmons's son Billy and his wife Renata, who were both shot dead. He then strangled and drowned their 20-month-old son, Trae.