[US] Prior Knowledge of Potential School-Based Violence: Information Students Learn May Prevent a Targeted Attack / U.S. Secret Service, U.S. Department of Education and McLean Hospital, May 2008
PDF - http://www.secretservice.gov/ntac/bystander_study.pdf
"This study serves as a follow-up to the Safe School Initiative (SSI). One of the most significant findings from the SSI is that prior to most school attacks, other children knew what was going to happen...."