Legally speaking, what could happen to him?
As a 16 year old he'd be a young offender so it would be a special youth prison.
I'm curious how a 16 year old had access to a chainsaw. My guess is someone - parents or friends - incriminated him.
Given he was 16, there's probably a good chance the muppet posted a video or picture on social media.
In some ways what happens legally is the least of his problems. If found guilty he will likely become as reviled as the cat bin woman:
https://www.theguardian.com/world/2010/oct/19/cat-bin-woman-...
Presumably a parent had a chainsaw, kept it in the garage, and the teen had access to the garage.
And 16 isn't that young - you can leave school at age 16 and start working full time.
A chainsaw is nothing compared to those, but you’d want some assurances they wouldn’t cut themselves (e.g. be large enough to handle it).
https://www.gov.uk/government/news/new-powers-to-crack-down-...