NYPD friendly fire

[perpetualponder]

Recently an off-duty NYPD cop was shot and killed by two on-duty cops.  The off-duty cop found a man breaking into his car as he came off duty and chased after him with his gun drawn. The on-duty cops got scared seeing a man (the off-duty cop) wielding a gun and perhaps turning towards them and one of them opened fire. I don't know details of the incident. Another off-duty cop was killed by an on-duty cop a few years previously.

I see two possible policies that might prevent such accidents:

1. Prohibit cops from shooting unless the other guy either aims a weapon specifically at them (not just turning towards them with weapon drawn) or actually shoots a third party and is unambiguously the aggressor.
2. Prohibit off-duty cops from wielding their firearms except in self defense, just like civilians.

Policy #1 would be more effective at preventing such accidents and civilians killed by cops but may risk getting cops killed by criminals. I wonder if anyone has done a quantitative evaluation of police rules of engagement.