A survivor of the Florida school shooting says the idea that killers can be stopped if people make friends with them is a "slap in the face".
Isabelle Robinson is a student at Marjory Stoneman Douglas High School, where Nikolas Cruz killed 17 people in February.
The #WalkUpNotOut hashtag has been used to suggest students should make friends with potentially dangerous classmates.
Writing in The New York Times, Isabelle says that is a "dangerous sentiment".
"The idea that we are to blame, even implicitly, for the murders of our friends and teachers is a slap in the face to all Stoneman Douglas victims and survivors," Isabelle says.
A campaign for stricter gun controls in the US has been growing since the school shooting on Valentine's Day.
That movement has been largely led by students from the school.
Hundreds of thousands of protesters took to the streets across the US calling for tighter gun control on 24 March in the March For Our Lives.
In the essay for The New York Times, Isabelle describes her first meeting with Nikolas Cruz when she was 12.
"I was eating lunch with my friends, most likely discussing One Direction or Ed Sheeran, when I felt a sudden pain in my lower back," she writes.
"I turned around and saw him, smirking... his eyes were lit up with a sick, twisted joy as he watched me cry.
"The apple that he had thrown at my back rolled slowly along the tiled floor."
"I don't remember if Mr. Cruz was confronted over his actions, but in my 12-year-old naivety, I trusted that the adults around me would take care of the situation.
"Five years later, hiding in a dark closet inside Marjory Stoneman Douglas High School, I would discover just how wrong I was."
A year later Isabelle became Cruz's tutor, helping him with work.
"Looking back, I am horrified," she writes. "I now understand that I was left, unassisted, with a student who had a known history of rage and brutality."
Isabelle goes on to say she knows the "benefits of reaching out to those who need kindness most".
But she says: "It is not the obligation of children to befriend classmates who have demonstrated aggressive, unpredictable or violent tendencies."
"No amount of kindness or compassion alone would have changed the person that Nikolas Cruz is and was, or the horrendous actions he perpetrated.
"That is a weak excuse for the failures of our school system, our government and our gun laws."