Shooter at Michigan State who killed three had no ties to school, officials say

Details emerge about shooting, in which shooter left note mentioned fatigue at being rejected' by women

The man who stormed on to Michigan State University's campus and shot three students to death before killing himself bought the ammunition fired during the attack only a few hours earlier, investigators announced on Thursday.

Additionally, authorities said, the murderer had no personal or professional connection to the school, making his motive a mystery to them, despite his leaving a note which - among other things - complained about feeling rejected and not having sex during the last decade.