Are 4 year olds sociopaths?

so·ci·o·path

ˈsōsēōˌpaTH/

noun

noun: sociopath; plural noun: sociopaths

1.

a person with a personality disorder manifesting itself in extreme antisocial attitudes and behavior and a lack of conscience

My youngest is 4 and I am bit worried he is a sociopath. He had an incident at  daycare last week where he pushed his best friend from the top of the play ground structure (6 feet in the air). The kid had to go to the hospital and have 2 stitches in his face. OMG 
From all accounts it was an accident and H did feel bad about it but still HOLY SHIT HE SENT A KID TO THE HOSPITAL and he is 4!

What is the proper procedure for this?

We talked about how hurting your friend was a bad thing and not to do it again. I also grounded him from TV for 4 days. I feel awful (worst parent ever?) and I am almost positive this kids mom works at the preschool we also go to. Can you say AWKWARD?