But...
How did he know the family would be in this particular park?
Did he stalk the family?
Weren't he afraid he would be overpowered by adults shortly after the attack?
I'm more and more convinced it was random attack by a disturbed individual.
Anything could have set him off.
And he attacked with what he had in his hands at that moment.
I remember when I was a teen,
one day as my friend and I were standing at the bus stop,
suddenly an older woman started throwing stones at my friend
and then ran away.
Why?
Nobody knows
JMO