I know at least one of our local agencies permits lethal force against a suspect who is not posing an immediate threat to officers or the public, but is moving "to a position of advantage" (if I remember the wording correctly) and there is a high likelihood that they will then pose a threat to officers/the public. The frequently-cited example is an active shooter that is currently running towards cover, but not actually pointing or firing a weapon at that exact moment. I assume that most of the others in the state have some sort of similar policy, but am just more familiar with this agency.
A friend of mine was one of the first on scene to a situation where this was utilized: a former Marine (and possibly former USBP IRRC?) was involved in some sort of altercation with his wife. A neighbor, an older, off-duty police volunteer (who did not carry a firearm as part of his police duties) came to the house open carrying a pistol and attempted to intervene on the wife's behalf. The bad guy disarmed the volunteer, killed him, and I believe killed the wife, as well. Police responded and surrounded the house, but the suspect was able to move to a neighboring house undetected. At some point he made a break for it, and was shot in the back as he was moving to a position of tactical advantage.
This video is a completely different situation as the suspect turns to engage the officer, placing him in imminent danger from deadly physical force; however, had the suspect not done so and instead attempted to board the "limo service" van that was parked on the street (assuming it was occupied), that might have justified shooting him in the back to prevent the danger to the occupants/position of advantage. Likewise, had the pursuit gone on and he had tried to enter an occupied row house along the street. Shooting people in the back who aren't actively firing rounds at that exact moment doesn't automatically equal bad, but there have to (and should be) heightened circumstances to justify it.
Now, whether or not I would want to justify such an action in a city with that outlook and that history is an entirely different matter...
Either way, good job by the officer for reacting in time (and, from the looks of things in the slow-motion replay a pretty quick draw stroke on the run as soon as he saw the weapon). I can only hope that the public realizes the danger this judge caused by releasing this guy and takes action by a recall or with their votes during the next retention cycle (if that's what Baltimore does), but I doubt they will...