Directed EMP pulse weapon. Interaction with bike frame and graphene inside his body. I think this was a test and came from across the street near or from a car parked at the gas station or in front of the bodega at the top right of the screen. The guy's stationary and just "falls over" which shows a no-notice and almost instantaneous heart stoppage. Usually, with a myocardial infarction or other "hear attack' the individual will clutch his chest in the classic "praying mantis" position before crossing the Rainbow Bridge. This attack shows nothing of that involuntary muscle movement perhaps demonstrating that his various muscles were also momentarily paralyzed by the pulse. If the weapon has any range to it I can think of all kinds of assassination scenarios in and outside.