I'm pretty sure that's Freddy. :P
But seriously, he certainly can't be "Sammy" or Henry would've mentioned him being with Charlie the day of the incident.
In fact, Sammy would've been stated to have gone missing after Charlie was murdered. But no, Only Charlie was the catalyst for Freddy's downfall.
And that one kid we saw with Charlie was clearly just another kid at the party.
She apparently found out that a certain "yellow rabbit" was up to no good and tried to save the kid from him, only for her to pay for it with her own life.
This man, however, was obviously the one whose voice we heard saying: "Half the town will be dead by morning" (it certainly didn't sound like Matthew Lillard).
So chances are he is actually evil and is most likely in cahoots with William Afton.
And if this is, in fact, "Jeremy Fitzgerald", then I do believe we owe the Puppet and the other animatronics our sincerest apologies! XD
