So you know that your two dog are aggressive, but yet you keep them around.
Like a time bomb.
I suppose in this instance the cop could have stood back and let these animals keep fighting until they killed each other, but he would have been criticised for that ,if he had.
When you have aggressive animals you must keep them away from the public or else they get what they deserve
“let these animals keep fighting until they killed each other”
Most dogs do NOT fight to the death; they have long inbred instincts that keep them from stopping short of killing another dog.
The fact that those mastiffs had not killed the smaller stray in the time from the beginning of the fight to the arrival of the police highlights that these dogs were not looking to kill the stray, just to establish dominance and make it explicitly clear that the stray was not to bother them again.