Nothing in this story indicates that a fatal shooting by an Arapahoe County, Colorado jail guard was justified. If further facts sustain this assessment, then it points once again to the falacy of the meme that law enforcement gun owners are risk free.
The man was a sheriff's deputy, so he presumably was taught when it is appropriate to use a firearm. There were many witnesses, so one can hope that the facts will come out. The family of the man killed has urged authorities to prosecute the deputy.