He has a Killing Shot that ignores LoS. Three time I was one shot by his killing shots while I was behind a pillar. Apparently he understands LoS because he tried to move to me if I am behind the pillar. The problem is, when he starts casting Killing Shot and you are in LoS at that moment, he will always shoot you even you are already out of LoS when he finished his cast and start shooting. If LoS is finalized at the start of a cast, it is pointless to move away from LoS.