The Spokane Serial Killer

Robert Lee Yates is the most prolific serial killer in Washington State history, with at least eighteen victims to his name. Mostly, these are prostitutes murdered during a two-year period in the mid to late 1990s in Spokane, Washington State. 
It is more than possible that we can trace the beginnings of Yates' murderous personality to before he was even born. His father, Robert Lee Yates senior, was one of ten siblings who grew up on a Tennessee farm. We know very little about this time other than, in 1945, his father – Robert Yates' Jr's grandfather - was murdered by his wife.

But what possessed Yates to go on a murderous rampage for years on end? And how was he finally caught?