Polo
I think he was afraid of me. I know he saw how much power I had, that I might surpass him one day. And when I found out that he'd been lying to me, I think he realized I wouldn't just follow him blindly anymore. That he couldn't control me like he did with the others. So he decided to get rid of me.
But he didn't really take the opportunity to explain himself. A bright green light just woke up in the middle of the night, and I turned to find him mid swing. Kylo Ren fought him off, destroyed the temple in the process. But none of it happened like people say it did. And Kylo Ren didn't kill me or any of Luke's other students that night.