The mother of a teenage boy who brought a gun to an Indiana middle school called 911 to alert authorities and school officials "to the imminent danger," the Indiana State Police said Friday.
The tipster's actions "likely prevented a lot of lost lives," police said Thursday.
The 14-year-old died at Dennis Intermediate School in Richmond from a single self-inflicted gunshot wound, preliminary autopsy results found, according to police.
The incident began when his mother called police around 8 a.m. Thursday to report potential violence at the school, prompting a police response and the building to go on lock down, authorities said.
After officers confronted the teen outside the school, the gunman "reportedly shot out the glass of a locked entry door" and ran inside the building, police said.
The teen, who was not a student at the school but lived in the area, exchanged gunfire with the officers as they followed him, police said.
No students were hurt, police said.
Because "someone knew something and said something," Indiana State Police Sgt. John Bowling added Thursday, "the school was able to follow procedure to help protect students."
Richmond Community Schools Superintendent Todd Terrill said students, staff and teachers -- who have undergone drills -- responded appropriately.