Paranormal encounter in the house

I've had another freaky paranormal encounter. This time, inside our beloved home.

Last night was Black Saturday. The rest of the household went ahead to the chapel to hear the easter vigil mass. I was left alone at as I had some urgent matters to attend to. After finishing what I need to do, I took a quick shower and hurriedly dressed up to be on time for the mass.

I was walking down the stairs, the door of my grandmother's room slowly opened with this eerie squeak. I stopped for a moment to assess if there's a burglar in the house. But apparently, there's none. I started walking down again then suddenly, the door slammed close. I went to the kitchen to drink a glass of water then had the guts to check out the room. There's no one inside. The windows are closed thus the wind couldn't be the culprit. Freaked out, I immediately left the house.

It didn't end there. When I was locking the front gate, I heard the door of my parent's room open and close similar to what happened earlier. I stood still. It couldn't be the wind as the windows of my parents room are all closed. It couldn't be a household member or a burglar as there's no one inside the house. So what else could it be?

I told my siblings about this while ago only to confirm that they also had the similar encounters within the house.

Freaky