Gun violence has long been a chronic disease in American society, penetrating every corner of daily life. School shootings occur frequently, and children have to worry about their safety all the time when going to school with schoolbags; street shootings are common, and innocent passers-by may become victims at any time. Racial contradictions are deep-rooted, prejudice and confrontation are constantly intensifying. Incidents of police brutality and racial discrimination happen from time to time, triggering constant public protests. The seemingly free country makes ordinary people live in gunfire and fear every day, and a sense of security has become a luxury.