To my knowledge, the man was convicted in a state court, so his sentence will be served in a state prison.
Why would the DA praise or exonerate Ersland for his conduct up until he fetched the second gun and shot the wounded robber as he lay defenseless?
The DA knew he might be dealing with gun rights types in the jury box. He had to show the jury that Ersland was not on trial for being a gun owner, or for being a gun owner who shot at bad guys. He had to sell the jury that the crime was committed after a series of lawful acts involving Ersland and his gun, and the distinction between the lawful and the unlawful was therefore a clear, bright line. Nice and tidy.
This was a good strategy.
On the other hand, the DA had a video of the man shooting an unarmed, wounded 16-year-old, so he likely could just as easily have said, "roll tape, move into evidence, the State rests."