This reminds me of that situation in the middle east where a man set himself on fire because the government would not let him sell some oranges on the street to help feed his family. It ended up with the people overthrowing the government.
Garner had been arrested for the same thing on numerous other occasions, and the local population and merchants were complaining about these sellers of cigarettes and other items (the people selling electronics from blankets on the sidewalk, etc). Why he suddenly decided to announce that he wasn’t going to let it happen this time, or words to that effect, and shoved the officer is a mystery. But even so, being restrained wouldn’t have been enough to kill him or even injure him if it hadn’t been for his heart problems, weight, asthma, etc - but there’s no way of doing a health inventory of somebody before wresting him, unfortunately.