I think we should be sympathetic because we have all done profoundly stupid things in our lifetimes, and outside the grace of God we would be just as dead. Also, these are teen boys, the most notorious dumb-thing-doers.
I would feel sympathetic if someone was killed due to actions beyond their control. If the roller coaster came flying off the tracks and landed on this young man, I would feel completely different. I cannot, however, feel sympathy for ignorance, fatal or not.
Let me illustrate.
Our thirteen-year-old son died as a result of a driving mistake made by his older sister, our daughter.
Did my son have no "Grace of God?"
Stop blaming God for the accidental deaths of people. God does not selectively choose people to murder as a gesture of his power to give or not give "Grace."
Who would worship such a cruel God?
If you have a thirteen-year-old son who is not killed in an accident, does he have "God's Grace" withheld from my son?
The world in which we live is flawed. It is full of accidents and illnesses that take lives. Our world is governed by laws of physics. For example, people can fall from heights and die because of the laws of gravity.
I do not believe God surveys the world every day and picks people to snuff just because He can.
He allows us to live with free choice in a flawed world. We suffer from both our own wrong choices and from the dangers of illnesses that can destroy us.