Hawkfrost is a evil Kitteh who every thought he was brought to Riverclan as was named a warrior straight away. But, here is what actully happened:

Hawkkit was brought to Riverclan with his sister Mothkit. Hawkkits mother was arguing with another she cat who's kit is also called Hawkkit. While they where arguing, Hawkkit killed the other Hawkkit, and grabbed Mothkit and made it look like she murdered the other Hawkkit. Mothkit got blamed but didn't die. So Hawkfrost, taking after his dad Tigerstar, ate him. Hawkfrost was later introduced as Hawkfrost to the other clans a few moons later. In most battles, cats bodies where never found because of Hawkfrost eating them. He also ate cats while they where alive, and was good friends with Gaystrip.