With hindsight in mind, it was whatever or whoever that distracted the black shirt guy was the cause of the two pedestrians' deaths. At the start of the video you see black shirt guy & jersey guy walk into camera view. Jersey guy turns to his right indicating his intention to cross the street while the light remains green. Something catches black shirt guy's attention, drawing him away from the intersection which in turn persuades jersey guy to follow suit. In the mean time another couple crosses the street. About 10 seconds later both black shirt guy & jersey guy walks toward the intersection but hesitates at the crosswalk for a few seconds due to a stale green light. The rest is a tragic history.
Two couples; one died, the other lived. One distracted by "city life", while the other walked toward the (green) light.