A school shooting or school massacre is when someone shoots a gun at students or teachers at a school or college. Many school shootings have happened in the United States. Very often, the person responsible for the attack is a former student or pupil., who had to leave the school. Most fo the time, school shootings are planned attaacks. When planning, the attackers either want to get a lot of media attention, or they want to kill or hurt as many people as possible. In most cases, the perpetrators will announce ("leak") the idea, either directly or indirectly.There are certin things or events that trigger such a schooting: The person will react to these trigers with anger, frustration or despair. The person doing the schhoting will often either commit uicide at the end, or they'll arrange the situation in such a way that they are killed by police, or other security forces.Research has shown that the perpetratros either want to kill or hurt fellow students, or they want to hurt teachers/professors; cases whjere both groups are targeted are rare. Most of the time, there is one attacker. Cases where two or three people act together are rare.