in 2021, we are seeing all the reopening kind of stressors. so we are seeing people going back to work. people going back to school. people spending more time outdoors, now, doing recreational and entertainment things. reporter: christopher herman also cites spiking-gun sales for the increase in homicides this year. and thinning, burned-out ranks of police departments. exemplified by an angry, exasperated sheriff, whose deputies battled those teenagers in florida. this is something i ve never seen, in 35 years of policing, and i m sad to say, thank god, my career s starting to come to an end because i don t know what the future of law enforcement looks like in this country. reporter: the spike in violent crime is so alarming that, after last year s movement to defund police departments. several-major cities, like new york, l.a., and oakland, are now scrambling to pour money, back, into their police departments. but experts are, still, warning us, we are seeing record retirement