In general your assessment is good. However, since the incursion was from the north and probably involved someone who was NOT a member of one of the favored ethnic groups -- that is, NOT Hispanic -- and since the agent only fired once, he should get off with under 10 years.
Had the driver of the SUV been Hispanic and had the border agent actually fired effectively, he'd be looking at decades of hard time.
What hold does the gummint have over these guys that they don't all quit? I'd LOVE to be a BP guy if patrolling the border effectively was part of the mission AND if you got commended when you did your job.
Unless he’s extradited to Canada to face war crimes prosecution, then he'll do 10 years.