My brother in law came home to find a completely different person in his house (update)

I don't usually post on here but feel like this is an appropriate place to post this. My brother in law (32, no kids, married) went to our house for some personal reasons and when he got there he found a completely different person in our house. He said that when he saw the person he thought it was one of our mutual friends (and his friend) so he talked to him until he saw his face and realized it wasn't him. He said he got really freaked out and left. We were confused on what he was talking about because we didn't invite anyone over, and our mutual friend was in another state, so I'm just wondering now if he went through a glitch in the matrix or something. Any thoughts would be cool.<br><br>Edit: to answer a couple questions that I have seen, 1 yes he had a key and, 2 he did do the normal things he does in our house like sit in the living room and look at his phone. Also the other day my mom went out for a drive and thought she saw my sister on the street smoking a cigarette, my sister had been at home when my mom left and she didn't have a car so she couldn't have been out smoking on the street. These events happened about 3 days apart so I thought it was weird.