Declan tapped on the orphanage door, when the owner opened to door he ate her. When he walked in, he cried of happiness because these children were going to be delicious.
The kids thought it was sadness but they fell right into his trap he ate them all within seconds, and suddenly, the room was empty. So Declan ate his legs and the grew back instantly. This was probably because of all the delicious protein the kids gave him.