You don't know if he has died upon disbelief. Some people and their actions might be of a unbeliever, but he belongs to paradise and some people their actions belong to believers but they are people of hell fire. This non-Muslim friend of yours, you do not know. You cannot say well he has died and for sure he will end up in hell fire. Only Allah knows that. However what we do have FULL trust is that Allah(swt) has FOR SURE showed His signs of there being a Creator to him, before he died. So upon what state he finally has died, we do not know. Maybe still did not believe in a Creator, maybe he did believe in a Creator. That is why i said, hope for the best. More you cannot do. The people who end up in hell fire, THEY themselves will be convinced they deserve hell fire. NO human being enters hell fire if they themselves are not convinced their place is hell fire. So lets say if this friend of yours will end up in hell fire, HE HIMSELF will first be 100% convinced he deserves hell fire before entering it. However again, we cannot make the judgement he will end up in hell fire. He maybe end up in paradise and you and i end up in hell fire. This possibility also exists. So he has died, this game (life) is over, you and i are still playing this game (life) and do our best to "win" this game (ie follow the path of Islam, and get rid of arrogance and pride, be humble, have patience, not do shirk, and keep away from sins and repent if we have done sins as we sure will still do more sins in our life time but again repent).