So there's a building, My guy is one side of the building, no windows, about 3 squares from the corner, the alien guy is on the other side of the building, about 5 squares from the corner. Another of my guys follows him round the corner. Fires, the dude survives (1hp of course). I'm expecting him to return fire at the guy on the corner. Instead he fires at the wall next to him, goes through that wall, through the building, through the other wall. Hits my other guy.
I might have been able to shoot him from my end but I didn't check because I had to kill someone else who was flanking him. Regardless of that, it indicated my guy was in full cover so he can't have been flanked by the guy on the other side of the building. It's most likely a visual bug where the walls had damage that wasn't shown or something.