I'm not sure WHY he's awake or even when he fell asleep last night, but Sam is already up for the day. Eric said they went for a super long walk. And normally, I'd wonder, but given the fact Sam was completely out when I got home at 8, yeah, pretty sure it happened.
The challenge with him going to sleep so early is that he's up early. Neither of the boys understand the concept of sleeping past a given number of hours. Honestly I'm surprised Henry's not awake yet, he was out by 630 last night.