His family says it's not true. People who were around and remember Alden say it was. My GMIL was in their ward and said that she remembers that he was a very evil young man. It's all up in the air. Take the book with a grain of salt, the lady who wrote it has had a lot of controversy over several of her books, but it's still an interesting read. I've read it like 4 or so time. Either way, it's a fun urban legend that PG has..
Rumor is that there was some sort of devil worshipping going on in the old bomb shelters underneath the school. I went down there a couple times when I was in school and can honestly say that some sort of cult rituals occurred underneath there, probably 20+ years before I went under, but people just left their stuff down there.