Press flag. It funny how the first time you get a hiding prompt in Spooky's Jumpscare Mansion is in room 810. Literally the second to last specimen, and you are JUST NOW hiding. The funny thing about Specimen 12 is that the old man here is not the specimen. The mansion is the real specimen. (Not Spooky's mansion, but a smaller fake mansion inside of the mansion.) The host is slow, and I mean SLOW, so he's not really an issue, which is a shame. The mansion is genuinely one of the coolest places in the game. Also, yes. The host is carrying a large sickle. If you try to hit him with the axe, he will just parry it.
Spooky's Jumpscare Mansion Man