It seems like a frequent occurrence but if you consider the number of interactions between the police and civilians, it's a low %. OTOH, once is too often.
The comment I have heard and seen most is "We were trained to stop the threat". I have yet to see a reporter comment on that- if they aren't moving and have stopped bleeding, the threat has been stopped. If the cops are using an entire magazine, it may be the extreme stress of the situation, but that implies most officers react the same way and it's not true- many officers are far more composed. The ones in Akron seem to have completely lost control.
I have major problems with the way a lot of people are shot by the police and it's time that we send the message that they need to stop firing when the person is running away UNLESS they're shooting at someone at the same time. In most states, we're told that someone whose home is being invaded should try to escape or hide, not just start blasting. Outside, a gun is required to remain in the holster or pocket unless it's going to be used- it's not legal to use it as a threat by holding it up or aiming at someone and this can be called 'brandishing', possibly resulting in being charged with aggravated assault. YouTube has plenty of videos of cops shooting at someone who they may not be able to see (the incident in Orlando is one of these and the officer fired at the guy with an Olive Garden restaurant directly behind the suspect). They clearly don't hit the target most of the time and in Akron, I would be surprised if the shell casings found total less than 100 whether they're all reported, or not.