Is there any particular reason to think such a thing couldn't happen in America, where rifles and explosives aren't hard to get? Mainly because gurs in general

Is there any particular reason to think such a thing couldn't happen in America, where rifles and explosives aren't hard to get? Mainly because gurs in general aren't hard to get in America. Any would-be shooter has to fear not only cops, but armed civilians. And if they are spanning an entire city and the police aren't able to keep up, you'd definitely get recreational hunters with their rifles trying to take them down.