something shitted all over my walls in my house.

was with a friend and we were downstairs hanging out then went upstairs into her room for 2 hours. Come downstairs and the house smells like shit and I see that something had diarrhead everywhere in the space under the stairs (that space is used as a laundry, the bin and cleaning supplies) No one else was home, all the doors and windows were shut so nothing could’ve come in. I think it may have been an animal? But it has to be a large one, and more so it’s probably still in the house. Wtf does one do in this situation. I wish I could post a photo