I suppose it depends on the state. If someone dies while you are part of criminal action, even if you are nowhere near the death you can be charged with what is called felony murder. If the cops shoot and kill your partner in crime, you can be charged. Might not seem fair, but if you weren’t breaking the law, someone would still be alive.
That said, I don’t know what the situation is regarding juveniles. Each state treats them differently. Sounds like NY turns them loose at 21 if they are too young to be certified as adults. New York appears to be eager to stop the “crime to prison pipeline”.
I grew up in Queens. In 1966, 15 y.o. black kid down the block stabbed a young Jewish man, who just returned from Vietnam, where he served as a infantry platoon leader to death.
1972, kid turns 21, and is turned loose. First thing he does is go down to the laundromat, where he grabs a small white kid and throws him into a dryer and starts it.
Nothing changes.