He was 15.
This is one of the MANY things I disagree with so called "justice" in our country (the USA) on. I don't know what others do.
If a 15 year old isn't old enough to vote because their mind isn't developed, they're not old enough to stand trial as an adult for a crime their under developed brain committed. The government will not consider them an adult unless it wants to prosecute them. It's pure hypocrisy.