When Chu Yunsheng's group arrived at Kelvin city, the city was already a mess. Ashe was about to lose Warehouse No. 59, which stored most of their supplies.
Vampires were not immortals, since the invention of guns, vampires were no longer unkillable. They would also bleed when they were shot, and they would also die.
As time went on, human weapons became more and more advanced, and always stood at the cutting edge of technology. No matter how strong the bodies of vampires were, and no matter how fast they were, once they were surrounded by people holding modern weapons, they would still be killed.
In the United States, almost everyone had a gun. Although civilians rarely had large-caliber weapons and heavy weapons, those small arms could also be extremely deadly once they accumulated to a certain amount.