Help! Why would my dog do this?

Our dog is about 2 years old. We adopted him about 6 months ago. He is fully house trained, and has run of the house all day while we work. He never has an accident.

On Saturday night, my in laws came over and we were out for about 3 hours for my daughter's school play.

We came home to find that he pooped on the rug in the den and lifted his leg and peed on my couch! Why!!!!!! He was not sick and he went out right before we left! My in laws stay in that room when they sleep over, my MIL even sleeps on the couch he peed on!

Could he see them as a threat?

Needless to say, he is no longer in my "circle of trust " right now.

Help! Why would my dog do this?

LOL, circle of trust.

Do they have any pets? He is becoming and adult and he probably feels like he is officially part of the pack. Or he ate before you left and didn't use the bathroom when he was supposed to so he figured he could kill two birds with one stone. I had an amazing chocolate lab who was a client of mine. I used to travel with him everywhere. About when he turned 3 I had him in a different clients house and he completely emptied his bladder on their rug. I was mortified. Male does sometimes do stuff like that when they are working out turf issues.

I am assuming he is neutered?