Sparks knows suspicious behavior when he sees it. And it wouldn't be unlike Biggs to hold out the information from Sparks that he's assigned some Heroes into trailing some criminals. Those two never really got along. So, when he spots a shadowy figure trailing someone - an armored, armed figure - he decides to cut that figure off at the pass. Suddenly, between Jack and the next roof is a marshal on his rocket steed.

He narrowed his eyes at the figure, trying to figure out who it was.

"So. Hi there."