Why did Rodger kill his roommates?

[muriel_volestrangler]

4. "These were the biggest nerds I had ever seen, and they were both very ugly with annoying voices"

"If they were pleasant to live with, I would regret having to kill them, but due to their behavior I now had no regrets about such a prospect. In fact, I'd even enjoy stabbing them both to death while they slept."

http://www.kwch.com/news/national/five-revelations-from-rodgers-twisted-manifesto/26168368

He'd also caught one of them stealing his candles, performed a "citizen's arrest", and had him charged for it:

The sheriff revealed during a news conference Saturday that in January, Rodger accused Hong of stealing $22 worth of candles from him. Rodger took the unusual step of making a citizen's arrest for petty theft and contacted sheriff's deputies, who arrested Hong. He was booked and released, but the two men evidently continued living together.

http://www.mercurynews.com/immigration/ci_25834727/three-fatal-stabbing-victims-santa-barbara-rampage-grew