Flocking with Predators

Modify the flocking model so that a button click randomly sends a predator across the screen. If a predator is near, then a boid scatters:

to flock
  find-flockmates
  if any? flockmates
  [
      find-nearest-neighbor
      ifelse distance nearest-neighbor < minimum-separation
      [
         separate
      ]
      [
         align
         cohere
       ]
   ]
   let nearby-predator one-of turtles with [predator] in-radius vision
   if nearby-predator != nobody [scatter nearby-predator]
end

to scatter [predator]
   ; quickly move safe distance away from predator
end