After driving the cartel cruiser to roof of the
parking garage in the mission you kill kenji, after the little cut scene, i
headed to portland, got my dodo from the I/E garage and flew over to the
staunton hideout roof.
You can snipe everyone along with kenji.
you can blow up all the cars too. but you need to
fly back to the ground and get into a cartel cruiser and enter the lower half of
the multi sytory garage for it to tell you you killed kenji... Just one of many
fun little mission twists you can do ;)