The who was immediately clear -- Everette did it. The why and how are now much clearer. Everette Simpson had experience.
According to The Associated Press:
He spent nine years in a California prison for second-degree murder of his first wife, who was hacked 16 times with a butcher knife in 1960, and 11 years in Louisiana for manslaughter of his second wife, attacked with knife and hatchet and then smothered with a pillow in 1983, authorities said.