Well, yes, it is all about proportions.
Blacks killed by police: 123 = 27.4% of those killed
Whites killed by police: 326 = 72.6% of those killed
According to FBI stats:
"69.3 percent of all individuals arrested were white, 28.1 percent were black, and 2.6 percent were of other races."
So, it looks like there is a very close correlation between how much your "group" has crime-related contact with the police and you being killed by them.
Are police "overkilling" people? Probably. Does it look related to race, at least from THESE stats? No.
http://en.wikipedia.org/wiki/Demographics_of_the_United_States
Around about 13-14% of the US population is black. The stats you show above mean that black people are both arrested (28.1%), and killed by police (27.4%), about twice as often as white people.
Comparing the actual numbers against each other is meaningless unless you take them as a proportion of total population.
Though only making up 13 percent of the population, they commit more than twice as many arrest-worthy crimes.