First of all a common security guard isn't supposed to use a gun, he's supposed to have a teaser only. Most people say that there's a spirit behind the trigger, at that moment you might be consumed with the power it gives you over someone else. But This is absolute garbage, no matter what must have happened taking his life wasn't the best way to go about it. He should be dealt with, murder is a sin against God and man. Jail should be a fair price for him but it should be life in prison so he doesn't get that chance to do that to someone else. Some people abuse a little power they have and try to oppress others with it
This is not the right way of handling such a situation. When someone is watching soccer along with a big crowd, there'll be noise. Another thing people can watch from home with utmost comfort, but they reach here to cheer and enjoy the moments. People will be drunk, and that makes them cheer and make more noise than a common soccer fan. Gambling and broadcast locations are getting to be murder locations. People need to realise that there need to be proper arrangements to keep things under control. In such situations these kinds of incidents could be avoided.