Indigo has some good thoughts, but I can almost feel your panic when you read "red flag."
You should explore his thoughts, though, before you decide your child is a sociopath. My son never said this the way your child did. But: He was asked why he did [X bad act to another kid], and he responded "because I wanted to." Bless the experienced, sensitive teacher that followed up on that, and helped him explain himself. In the end she showed us that he didn't mean "because I wanted to" but rather "because I had to." This was when we first started to understand that he didn't have the tools to stop himself.
I think his impulse control would have improved anyway, because he's NOT a sociopath. But that teacher's skill helped him understand himself, and push himself the right way, with the right objective. Not "Just don't do it." Rather "Take responsibility to keep yourself away from that flashpoint. Recognize the signs, find the trusted adult, find a way to stave off the feelings."
Anyway - my two cents.
