Yeah, I was really surprised about Johnny Lewis.
I obviously didn't know him and didn't really follow his career any after he left SoA but I remember reading an interview with Sutter explaining why the character was killed (Lewis requested to leave the show to pursue other acting opportunities). He was really positive about the guy and how much he liked him and said if anyone else was considering him for a role he would give him a recommendation.
The next thing I hear is that he killed his 81-year-old landlady, possibly while high on drugs (TMZ), shortly after being released from jail where he had other charges pending. It's a tragic ending to a guy who showed a lot of promise as an actor.