What is the name of this Sci-fi anime movie?

Back in the 90's i watched a anime movie on the sci-fi channel. It was about a young boy about the age of 13ish who witnessed his mother being murdered. His mother was murdered and left for dead naked in the winter snow. A little later on in the movie the boy and his gang of friends are being chased i think for stealing something. He runs into a group of people i think are theives or some sort who take him on their ship to aveng his mother. When he meets up with the guy in his fortress who killed his mother he sees on the wall in a frozen block above the fireplace his mother naked. Any input is appreciated.