Leo & Gwen

Why is Leo so willing to allow Sarah to fry & to be led to the guillotine with how he had put it to Gwen, given that no knew as to what Gwen was getting rid of, much less Leo knowing what Gwen was getting rid of at that time?

Plus, there’s this: With how Leo had the mask & that he, himself had put it on, why think that Gwen wore it that night. When Gwen could have told him where the mask was for him to wear that night & killed Abigail, remember, how he freaked when he learned that the murder weapon that was proven to have been used on Abby is still in his possession?