It is dangerous because it involves a lot of driving, not because they are likely to get killed by a criminal. It is ranked 14th most dangerous job in the US, again, mostly because of traffic accidents. It was even lower in the past. There are plenty of more dangerous jobs that do not get free rein to murder people and keep their jobs or just move one town over. There should be two options if they kill someone and it is found to be unnecessary: They are arrested, or if they made a mistake but it was "reasonable" they are banned from working in law enforcement. Many instances of LEOs moving from town to town escalating conflicts until they get to kill someone, then repeating again somewhere else. No other profession has that amount of leeway for massive mistakes; accidentally killing someone and getting a slap on the wrist vs any other profession having an error of 1% that magnitude and getting fired.