Loud Sound from the Freezer After News of Great-Grandmother's Death

It happened in March 2018. My mother and I came to visit my grandma and grandpa in a village. In their yard there are three structures: what they call the winter kitchen, the summer kitchen, and the house itself. The summer kitchen is a very small space with a stove and a table, they cook there. In the winter kitchen they hang out when it gets cold and also cook food there, fire up the stove, essentially it's also a house, but small, there's a small guest room where usually one of the relatives stays, and a room with food supplies where there's a freezer where they keep meat and dairy.
In the evening grandma went to my great-grandmother's on the next street. She was over 90 years old. By then her legs had given out, and grandma went to take care of her. It was obvious she was dying. So, we stayed at their place in that very winter kitchen. Time around midnight. We're sitting with my mother in the guest room. Grandma comes in and tells us that great-grandma died. Naturally we're fucking shocked and then decide to go to bed. When grandma leaves, we lie down on our beds, turn off the light, when suddenly we hear a VERY loud sound from the next room, as if someone lifted the freezer door and slammed it down on top, we jumped up from the shock, mother went into that room and didn't spot anyone. It couldn't have opened by itself, I think you know what such freezers look like. What it was, we still don't know. It's creepy that it happened after the news of a relative's death, but I don't want to believe in ghosts. I'm sure there's some explanation for it, but what..?