From Real Life Villains Wiki
Weis Markets is officially Columbine High School.
~ Randy Stair announcing his intent to replicate the Columbine massacre.
Copycats will usually copy a behavior role from others they idolize or similize themselves with.

For instance, Parkland shooter Nikolas Cruz said through a video that they are going to be the next school shooter making an attempt to kill more students than the other previous school shooters. Other shooters may copy shootings like from the 1999 Columbine High School massacre and recreate it by wearing the same stuff or recreating the chaotic acts; Randy Stair is a good example of this. Also, the original shooters like Eric Harris and Dylan Klebold (who have been looked up to a lot by the newer school shooters) often made anti-semetic jokes referencing Nazis/Adolf Hitler, and were inspired by the movie Natural Born Killers.

However, copycats are not just limited to mass shooters. There have been documented cases of serial killers attempting to copy other serial killers. For example, the Zodiac Killer has inspired a number of other serial killers, such as Heriberto Seda, who called himself the New York Zodiac Killer.