If aliens came to the world the people would have no clue.The first reaction people will give is that my God is that a Alien’s ship people would start to lifestream in there phones some of them will click photo and some of them will run for home because they don’t know what will happened people will start to call police and stuff and police will be also shocked because they have never seen any alien.But when aliens will start to kill humans the Panic will begin all people will run for their life it will be chaos. Military would be informed and they have to keep the doctors and scientists safe from aliens the military would take the scientists to a underground bunker that has all the stuff that they need. Police would try to kill the aliens but would fail. Military army would try to kill them too but would be fail because they don’t know what kind of weapons would kill the aliens.Almost all the human would be killed but the people who have lived would try there best to survive and in the other hand the scientists would order military army to trap a Alien so they can run a experiment. I would be be hard to trap a Alien but if they managed to do it scientists can put a end to the alien they could make weapons to fight the aliens but they would have to do it quickly. If they manned to do it I am sure people would defend the aliens then the would have to start human civilization again.