Please remember that the Fourth Amendment protects us against unreasonable search and seizure. Sometimes, under exigent circumstances, action might need to be taken with the understanding that the reasonableness of that action might have to be justified later on.
"It is long been a principle of ours that one is no more armed because he has possession of a firearm than he is a musician because he owns a piano. There is no point in having a gun if you are not capable of using it skillfully." -- Jeff Cooper