Numbers

Two black men, one in Louisiana and one in Minnesota, were shot and killed by police officers earlier this week, and Black Lives Matter protests popped up all over the country. This morning we woke to find that the demonstration in Dallas led to eleven policemen being shot.  Five are dead and three more are listed as being in critical condition.  None of them had ever shot another human being in the line of duty.

There are, according to the National Law Enforcement Memorial Fund, 900,000 sworn police officers in the United States. The Washington Post, about the only one keeping track, reports that there were 990 people shot dead by police in 2015.  That means that only about .01% of peace officers were involved in shootings - justified or otherwise. 

Of those, police were responding to an attack in progress in 770 cases. 93 of the victims were unarmed and 34 were brandishing some sort of toy weapon. The Post does not differentiate between those actively involved in felonies and those who were simply in the wrong place at the wrong time, but we have to assume that most of those killings were justified.

Of those killed by cops, 948 were men -  494 were white, 258 black and 172 Hispanic.  That does mean that blacks were killed at a higher rate based on their percentage of the population, but it is also a fact that blacks commit more crime per capita than their white counterparts.  
It is worth noting that there were 123 police officers killed in the line of duty in 2015.