An hour later he called me back on Facetime except this time it was two kids (I could see them) speaking with what seemed like a eastern European accent. For different reasons I thought they were his visitors so I just sent him a message that two kids were playing with his phone and had called me and called me "bitch" :-)
I tried calling him back, he received the call, didn't take it but we confirmed (in another channel) that I had called him.
The two kids however called me back and asked me to stop calling them because their dad would come soon(!) This time however they had covered the camera.
Both of us have verified that we don't have any unknown devices.
I've now been searching twitter for news but no known hack.
Any hints on how to fix this?
PS: some more details. I have three numbers stored for my friend, one from central Europe, two local (i.e. Norwegian), and only one of them is in use.