We are going down a slippery slope if we are going to charge people for accidents let me provide an example.
For those that don't know there is a professional wrestler that goes by the name of Rey Mysterio Jr.
A few years ago during a tag team in Mexico Rey Mysterio performed a drop kick on another pro wrestler by the name of Perro Aguayo Jr.
Perro Aguayo Jr fell onto the middle rope, broke his neck and died as a result of that drop kick, you could say Rey Mysterio killed Perro Aguayo Jr.
Do you believe Rey Mysterio should have been arrested and charged for something that was clearly an accident because another person died?
If no why is this different? What happened to Perro Aguayo Jr was an accident Rey Mysterio had no intent to kill his opponent.
What happened to Adam Johnson was also an accident I do not believe for one second Matt Petgrave thought to himself "I'm going to kill this man" and then went out and did it.
I don't believe there was a sred of intent I believe just like the Perro Aguayo Jr incident, that the Adam Johnson incident was a freak accident with NO intent to kill whatsoever.