posting on dead brothers account

so my brother passed away around 6 years ago and just this morning someone went on his Facebook profile and posted a picture. I don't even know who could have done this...i asked the girl my brother was married to and it wasn't her. I didn't think it was her anyways because he is now married to somone else but it didnt hurt to ask. we don't really keep in contact with my brothers father side of the family so I guess it could have been one of them but idk. another thing is right when he passed away there was someone posting on a different Facebook account of my brothers. I know it's just a picture (a really crappy one because it's all pixulated) but still I don't think it's right for someone to do that....