No, he loved Squirrelflight, but was denied because she chose Brambleclaw over Ashfur.
Ashfur's murderer is Hollyleaf. Leafpool found a tuft of Hollyleaf's fur snagged in Ashfur's claws.
After the events of Long Shadows, yes, Ashfur dies, presumably murdered by his former love. he is murdered by hollyleaf
Hollyleaf
Hollyleaf
no one
No, Hollyleaf did.
No, Hollyleaf does. It may seem like Squirrelflight did but she didn't 'cause Hollyleaf admits that she did kill Ashfur in Sunrise.
Hollyleaf was the cat who killed Ashfur. She did so to protect her siblings and keep their secret from being exposed.
Ashfur-Revenge
It depends on what you think evil is. Hollyleaf does kill Ashfur though.
Hollyleaf hollyleaf[for certain-positive-sure]
No, Ashfur would never try to kill Squirrelfight. He loved her but tried to kill Hollyleaf, jayfeather, and Lionblaze to get revenge on her. Then she revealed they were not her children and he didn't kill them.