system
Given the following post, respond as if you're commenting on Reddit:
human
[WP] I am a stormtrooper serving on the ISD Devastator. Lord Vader summoned my fellow stormtrooper and myself to his chambers, cut my friend down with his lightsaber, looked at me, and then told me to get back to my station. What just happened?

Title explains it all. Why did Lord Vader cut my friend down with his lightsaber? We're just stormtroopers. We didn't let any rebels escape.

I thought he was going to kill me, but he looked at me for a few seconds without a word and told me to get back to my station. I obviously did as he told me to do.

What happened? Why? I have so many questions.
gpt
Using the available evidence, he'd narrowed the possible traitor down to just two candidates. When he called you before him, you were probably feeling nothing more than mild trepidation mingled with curiosity; you didn't know why you were there, and were expecting some kind of orders.

Your friend was the traitor, and no matter how good his deadpan Vader could sense this fact from his emotional state. Justice was swift and merciless.