SPOILER: There is a scene in the closing credits: Sam and Peter make a memorial for Detective David, Peter states that they must hide from Spooky Joe and the recently-revealed Moon. Sam says he knows and he'll be waiting.
SPOILER: There is a second scene at the end of the closing credits: Moon taunts a prisoner, revealed to be Jayden from School: The Last Stand (2015). Jayden warns Moon that he might escape, but Moon says that he'd ruin the plan, stating that anything could happen.