Everything was going great today. Just restarted my character. Finally got my mods figured out. Skyrim is running smoothly. I had just earned property to start building Lakeview. I fast travel to Riverwood for lumber, because I can never find the guy in Falkreath. I get there and I see something attacking the villagers. I figure it's dragonborn related or vampires. I get there and it is an npc I had never seen before. He was wearing plate armor. I thought to myself " I didn't add this npc and that is not something I would have added to my game. I go to attack him and he one hits me with his hammer. That was really out of place. His name was like Sgt something. Later I took a look at all my mods and none of them have him in the discription. Most of my mods are either craft items, some followers and the rest are homes.
Is it possible that he was another player in my game? Has this happen to anyone?