Today had this sitiuation where I had to inspect my work friend job, he did some mistakes so I've sent few pieces back to get made by another person, then few more and few more. Few hours after since he was working near he asked me - are you sure you checking them good? since the team leader was near I asked him before about it and checked few bits of that job so I told my colleague that team leader also checked. He got instantly mad on me and after few arguments he shouted to me Fuck off, fuck off. This was first time I've got into this type of situation and I feel really bad and don't know what to do. This person was my friend, I had a good relationship with him at work. Now It will give me more pressure as I'm already short on work friends. I'm 21 and also living in foreign country, could I get an advise what would you do in this case?