Early Warning, Timely Response-A Guide to Safe Schools
A Guide to Safe Schools Identifies both anger and aggression as two of the many warning signs.
http://www.air-dc.org/cecp/guide/

Guide for Preventing and Responding to School Violence
This site includes prevention guidelines, threat assessment, crisis planning, legal considerations, media recomnmmendations, legislative issues, etc.
http://www.theiacp.org/pubinfo/pubs/pslc/svindex.htm