Take the case of the Boston Marathon bombers.

If the authorities have advance knowledge of what these two (presumably only two) guys are up to and at the point where, say, they are carrying the explosive laden pressure cookers to the site—do you have to wait until they actually blow one or both of them up and kill a lot of people before taking whatever action is necessary to prevent them?

Or can you attempt to take preventive measures?

The ethics seem pretty clear to me.

If you can prevent someone from killing a lot of people and do not take action to stop them, you are as morally guilty of mass murder as they are.

If the government becomes aware of a mass murder plot and does not take measures to stop it, some people—often the very same people who protest government action—would blame the government for NOT stopping the plot in its tracks.

Let's get real, folks!!

Don Firth