Who did hawkfrost kill?

Hawkfrost becomes deputy of RiverClan after Mistyfoot goes missing.

Hawkfrost is a blood and power thirtsy cat. He is the son of Tigerstar and Sasha(a rouge). He had a brother: Tadpole before his mother Sasha took him to riverClan. Tadpole dies when he was a kit from drowning. Hawkfrost has a sister named Mothwing who was a medicine cat and two half-siblings named Brambleclaw and tawnypelt.