My uncle seen the three headed dog that guards the gates to hell?

I cannot pronounce the name so I will not type it he was in the basement working down there when he felt like someone was looking at him he turned around & there it was he ignored it thinking it was from lack of sleep. But he turned around multiple times & it was still there in the corner of the room he finally left after about an hour. My eight year old niece not hearing or knowing anything about this said there were men with guns in her room that said they were going to hurt them she will not go back there now. I am just worried because these are evil spirits obviously not just lost spirits looking for their place. My aunt who just got a steal on her dream home thinks it is imagination all the way around which she is the type of person who would not say anything because she has put "alot of work" into the home. I feel that I should be worried for them especially my cousin being so little & nobody listening to her. Please tell me if anyone has had these types of experiences with the three headed dog or is at an evil omen? I was thinking of having me & my mother go in there when nobody is there & doing some e.v.p's tell me what you think thanks for any feedback :) !