After a teenage gunman killed 17 people at a Parkland, Florida, high school last month, schools across the country were hit by a wave of copycat threats.

In Colorado, at least two high school students were arrested based on information sent to the state anonymous tip line and mobile app, known as Safe2Tell. “They had a list, they had weapons, they knew exactly what they wanted to do,” said Colorado Attorney General Cynthia Coffman, whose office administers the program.

States across the country are responding to high-profile school shootings and rising teen suicide rates by creating tip lines modeled on Colorado’s. The programs aim to prevent young people from behaving dangerously, whether that means bullying, using drugs or killing someone.

Coffman told PewTrust that Safe2Tell has saved lives in Colorado, and that such a system could have prevented the Parkland shooting. Nikolas Cruz, the expelled student who has admitted to shooting his former classmates at Marjory Stoneman Douglas High School, had a long record of disturbing behavior.