I grabbed a quick clip showing this player shooting me through a wall:
https://www.youtube.com/watch?v=q6cpUDcNLE4 (Not sure why quality is so poor)
This clip it is VERY obvious. There are no windows or any way for the player to know the spot I'm in.

Their profile on BF4DB had a video from another play too which shows behavior that looks very much like wallhacking:
https://www.youtube.com/watch?v=-KJTAmzI5yE&feature=youtu.be

Edit: Server I was on almost everyone on the server voted yes to ban then, and they were banned. Many people think this person is a cheater.