Aaron Stark now works to raise awareness around why mass attacks happen.

Aaron had a chaotic and violent childhood, and by the time he was a teenager he was homeless, angry and traumatised. At his lowest point, he began to plan an appaling act of violence in a bid to punish the world around him. He wanted to get hold of a gun, but before he could, his best friend Mike changed the course of his life with a small, simple act of kindness.

This episode includes themes of suicide, self harm and drug use.

If you need support relating to any of the issues we've covered in this interview, you can find more information on the BBC Action line website or at Befrienders.org

Presenter: Jo Fidgen