[There's nothing else he can do, nothing else he can say that he hasn't already...and there's no fixing this.]

I'm sorry. Come sit with me, love.

[He can do this, at least, arrange them so he's sitting with Caleb's head or shoulders in his lap so a hand can brush through his hair. Caleb deserved better than Chris' paltry ability to comfort, but he'd try.]

I know you'll be okay too, but it's okay if you're not that for a while as well. Grief takes its time.