That was not near enough proof to warn you. If you were still hitman, you did not job abuse. If you switched back to your previous job straight after you killed him, that deserves a warn.
My Conlusion: DO NOT Demote Silent, but do give him a verbal warning about this. Because that was not nearly enough evidence to warn. But keep Silent around, because he is a pretty good mod overall.
Just my opinion on this.

That was not near enough proof to warn you. If you were still hitman, you did not job abuse. If you switched back to your previous job straight after you killed him, that deserves a warn. My Conlusion: DO NOT Demote Silent, but do give him a verbal warning about this. Because that was not nearly enough evidence to warn. But keep Silent around, because he is a pretty good mod overall. Just my opinion on this.