Did he know it was Kylar, or did he simply wanted to kill a Sa'kage wetboy?
i reckon it was either more convincing to actually kill him or he did it just because he wanted to. the Ursuul murder gene kicking in so to speak.
I'm believing that it was so there were no loose ends.
Tenser killed Kylar to gain access to the hole that Logan was in. The quickest way to get thrown in would be to kill a Noble. But I assume being an Ursuul, he decided to actually do what he was getting thrown in jail for. Which is why he actually killed Kylar.