wow.. kids CAN be really into everything.. but this sounds too much.. in the case they even allowed the kid to throw crayons at a "stranger".. I mean why wouldnīt they corrected the kid?.. no wonder the house was like it was...

not to embarrass my own.. lol.. but heīs also 7. he has peed on his bed (while sleeping).. but nothing a good laundry and a lil scrubbing to get rid of it.. besides it was an accident.. although ONE time.. he was too busy playing he peed on his toy box.. yeah .. good thing itīs plastic and it was empty.. but it was that time ONLY..

as for crayon art.. well.. Iīve found art here and there.. but what one consider "normal".. hey, I did it too.. lol.. my kid has made happy faces and maps in walls (pencil thank God).. he did used a marker once but this time he drew on the underside of a coffee table.. and the most recent the highlighted my momīs mattress.. haha.. just colored a lil flower in the pattern

so itīs not like the house was covered in graffiti .. but a lil discipline and learning from them goes a long way.. by your description this peopleīs kid sounds like a lil brat.. and yes, i know some kids can be more "desctructive" even when parents DO teach well.. but this doesnīt seems the case