Personally, I don't necessarily have qualms about charging a juvenile as an adult, but I don't know anything about this particular situation to make a blanket judgement in this case
but, it is well-documented that teen-agers' brains are not as fully developed as adults' brains, and that one of the last parts to develop is the part that controls impulsive behavior - that is certainly not an excuse for what this young man did, but is something that should be taken into account and is part of the reason the juvenile system exists at all
Bad behavior
Although teens' brains are superior in some ways, they're distinctly immature in one key area. The last part of the brain to fully connect up—well past the teenage years—is the frontal lobe, which houses judgment, insight, dampening of emotions and impulse control. Since it isn't fully developed, there's a cognitive chasm between coming up with an idea and being able to decide if it's actually a good one...
https://www.childrenshospital.org/dream/summer08/the_teenage_brain.html