Police Activity has a video showing not just the shooting, but the lead up and aftermath.
It shows the desperate struggle of 6-8 officers rendering aid trying to save his life, and the near breakdown of the officer who shot him.
But its flagged to all hell and you're not even allowed to use the share function.
Looks like the kid was trying to toss his gun, and wasn't too smart about it. Takeaway: if you are holding a gun, prepare to get shot.
Not sure what the kid could have done differently. Maybe keep it in his pocket and keep his hands up and declare it to the officer once tensions have cooled? Hard to say.
He could have abandoned the gun in the ally way in plain sight for the police to see, then tossed his hands up and stood still. That might've been enough to save him.