"Things get made up and passed along," Salter said. "Later, a totally different picture emerges."
She said Columbine High School shooters Eric Harris and Dylan Klebold bullied others, as did two other school shooters: Kip Kinkel, who killed two students at Oregon's Thurston High School in 1998 after killing his parents; and Andrew Golden, who shot five people alongside Mitchell Johnson at Arkansas' Westside Middle School in 1998.
"The truth is, they were not bullied," said Salter, who holds a doctorate in clinical psychology and public practice from Harvard University and is a consultant to the Wisconsin Department of Corrections. "School killers were more often bullies than bullied."
Although many perpetrators of shooting sprees at schools were depressed, Salter said many others grew up in stable homes, had friends and were not the loners many people assumed they were.
But there often are signs of the impending crime, she said. A potential shooter might brag to students about making a plan to kill others. Other possible indications: a child trying to make a pipe bomb at home, or writings by children or teens that involve fantasies about killing.
Salter said 80 percent of school shooters provided some clue they were planning a massacre.
"The more specific the plan is, the more likely they are to do it," she said.
Salter also warned that if someone sends a text message that "something big is going to happen," or "stay out of the cafeteria at a certain time," authorities should be alerted.
One audience member at Thursday's keynote address recalled an incident when a Roy High School student did just that. After receiving troubling text messages from a friend in January 2012, the student alerted school authorities, who discovered that two teens had made a plan to bomb the school during an assembly. While no explosives were found in the teens' homes, authorities did find plans for an explosive device, along with maps of the school and its security features.
One of the teens served time in a juvenile center, while the other, who was 18 at the time, spent 105 days in jail and was placed on probation.
Reed Richards, chairman of the Utah Council on Victims of Crime, said the annual conference brings experts such as Salter to Utah to help educate law enforcement, prosecutors and victim advocates about the challenges and problems facing the legal system and their impact on victims.
Richards said prosecutors or law enforcement are often more focused on "getting the bad guy" than on the bad guys' victims. Such conferences, and other types of training, can help those who work in law enforcement and the legal system refocus on the victims.
"The person who really is hurt is the victim," Richards said.
Other topics addressed during the two-day conference, which was held in Midway, included prosecution of domestic violence crimes, cyberbullying, elder abuse and human trafficking.