...BA-253 looks at the lightsaber and takes a minute to think.
If he was to go after Obi Wan and cut him down, then he can return to normal life and have a very powerful ally in Darth Vader. However if he was to refuse, then he has to suffer the consequences of what happened earlier in the story plus Darth will be angrier with him than ever.
This decision is made all the harder by the fact that Obi Wan attempted to save him earlier and stuck up for him when all looked bad.
What is BA-253 going to do!?