Who helped Hawkfrost when he tried to kill Firestar?

Ashfur was the cat who helped Hawkfrost try to kill Firestar in the last book in The New Prophecy Series, Sunset. In the fifth book in The Power of Three Series, Long Shadows, Ashfur reveals himself to Squirrelflight, Jayfeather, Hollyleaf, and Lionblaze as the one who attempted the murder. He was furious at Squirrelflight and wanted her to feel the pain of losing a loved one like he when she left him to be with Brambleclaw.