There were so many questions after 17-year-old Ely Serna brought a shotgun to his Ohio school and opened fire in 2017, wounding two.
Along with the whys, West Liberty-Salem High School assistant principal Andy McGill recalled thinking, "Is there something I missed?"
"I never would have thought in a million years that it would be that person," he said.
The questions now focus on how to prevent anything like that from happening again. Schools like McGill's have been setting up teams to assess threats posed by students who display signs of violence, like another Ohio student, Connor Betts, who compiled a "hit list" years ago in high school and went on to kill nine people in a weekend shooting in Dayton.
In the 2017-2018 school year, 43.7% of public schools had threat assessment teams and 49.3% had systems for anonymous reporting of threats, according to U.S. Education Department statistics. They consider concerns raised by other students, school community members and even people commenting anonymously through tip lines.
"They put the pieces together and look at all these moving parts together, put the puzzle together," said Mac Hardy, operations director for the National Association of School Resource Officers.
"The parents are interviewed by a school counselor. Are there weapons inside the home? Where are they kept?" Hardy said. "There's a whole list of questions that they discuss. The teachers have a list of questions that they respond to in writing. You get a lot of information when you do this correctly."
Serna's attorney blamed his actions on mental illness, saying he believed he was following a deity's orders.
Despite consensus on the approach's benefits, school officials say they are limited in what they can do by privacy concerns, a lack of resources and limits on what they can communicate once a student leaves school.
Betts was suspended for compiling a "hit list" and a "rape list" during his junior year at Bellbrook High School, former classmates told The Associated Press on condition of anonymity out of fear they might face harassment. Bellbrook-Sugarcreek Schools wouldn't release information about Betts, citing legal protections for student records.
The goal of screening programs is to not only flag and address threats raised by students, but also to track and manage any risk they might pose. School districts are encouraged to set up a threat assessment team including at least a school administrator, a mental health professional, and a law enforcement representative.
At Hilliard City Schools in Ohio, the district uses a network of trained students, Superintendent John Marschhausen said. After Hilliard Davidson High School student John Staley was arrested in 2016 for plotting to attack his school, the district began requiring a mental health evaluation before it allows any student who has exhibited troubling behavior to return to school.
Marschhausen said the district does whatever it can to get students help but said that privacy laws can make it difficult to keep up the support beyond high school.
"One of our challenges as a society is - we have learned that with these young people who need support - it's a journey," Marschhausen said. "It's not like you take an action and you're cured."
Schools are coming under pressure to have threat assessment systems in place because of new state laws and court rulings that have held school systems liable, according to Stephen Brock, a professor at the School Psychology program at California State University, Sacramento.
Students who engage in threatening behaviors need to face consequences, but any disciplinary response must also be accompanied by intervention to address the root causes, Brock said.
"There are a number of different explanations for why someone might engage in an act of violence and what we need to do, if the person is not an immediate risk, is begin to figure out why," said Brock.
Success stories cannot be discussed because of student confidentiality, Brock said, but he said interventions have prevented far more tragedies than those that have occurred.
Still, it remains unclear how widely the protocols have been implemented in communities around the country.
Schools need significant resources and commitment to set up effective prevention teams, said Joshua Starr, CEO of PDK International, a professional organization for educators.
"Whether or not a school board or principal actually follows through, I don't think anybody knows," he said.
Schools are not completely responsible to follow up on treatment, but rather must assess the credibility of the threat and make referrals to professionals for more thorough evaluations, said Ken Trump, president of National School Safety and Security Services.
Superintendent Jennifer Hefner of Alexander County schools in North Carolina said the district will have a threat assessment team for the first time this school year with school representatives, law enforcement, counselors, social workers and others.
"We are ready to implement the team, but we hope it doesn't happen," Hefner said.
McGill said his district's threat assessment team is set up to work with outside agencies and law enforcement to address both the immediate and long-term consequences on students and the entire community.
"There are so many pieces to it," McGill said. "It can be overwhelming trying to think about the entirety of the situation and the broad scope of the situation but it's really something you have to do."
McGill is happy to see more attention being paid to the mental health of young people, saying the more schools understand brain health, the better prepared they will be to usher kids to adulthood. "It's something we're figuring out," he said. "We just need to figure it out faster."
Associated Press writers Michael Melia in Hartford, Conn., Julie Carr Smyth in Dayton, Ohio, and Michael Biesecker in Washington contributed to this report. Waggoner reported from Raleigh, N.C., and Thompson from Buffalo, N.Y.