Wait, Saul couldn't have. Because whoever it was they assassinated Durai. And Saul is a terrible shot when sober, also bear in mind that Saul was drink at the time, and Lizzy was with him.

I don't want to say it, but perhaps Lizzy took Saul's gun, and Saul didn't tell the others it was her since he loves her and will protect her. And Lizzy is a really good marksman so she could have killed Durai.