Who is the murderer in The Egypt Game?

April
and her friends live in a neighborhood that has many children. This would suggest that the
neighborhood is quite safe. Unfortunately, two children have been found murdered, and the
murderer is completely unknown. The reader is led to suspect that the murderer is the reclusive
Professor; however, that ends up being false. The murderer turns out to be a relative of Mr.
Schmitt that struggles to find work. Readers are told that something is mentally wrong with the
man, and that explains why he can not seem to keep a job. Mr. Schmitt feels obligated to help
out a relative of his, so Mr. Schmitt always agrees to let him work as a stockboy for a
relatively low amount of payment. The man will work for a bit, earn some money, leave the area,
and return again.