You are approaching matters (asking the question) from a European perspective whereas in the USA they have their own perspective and reactions. Both there and in Europe cultural mindsets govern. In the USA it is widespread to consider it natural to reach for a gun when alarmed in any way, in Europe that is very much the exception. Poverty is more widespread and entrenched in the USA and that impinges on much of life for very many. It is not entirely ridiculous to suggest that the "wild West" mentality is still echoing through society there and affecting some responses to situations. Americans are widely regarded as being less reserved than Europeans and they thus show/enact reactions more noticeably than Europeans and at some point a herd mentality (including forms of hysteria) set in - the "flash point" is perhaps significantly lower in the USA than in Europe, but a flash point exists in Europe and probably everywhere, just at different levels.