My aunt experienced something similar. She was home alone, when she heard someone open the door snd walking in the hallway. Since her husband (my uncle) was not supposed to get home in a few hours, she went downstairs to see if someone was there.
She did not see anyone, but outside the door she saw footsteps in the snow leading to the door, but not away from it. This got her nervous, and on a second glance she saw a unfamiliar pair of shoes in the hallway. She ran up and called the police, and when they came and searched through the house, the found a homeless man hiding in a storage room, holding my uncles shotgun, but luckily he had not found the ammunition (it was hid another place).
He was arrested, but according to my aunt it is the scariest thing she has ever experienced.
