Adapting the Stamford incident

Markus and Stephen McFeely also talked about what sparks the entire Civil War. Of course, there is a continuity between the events of The Winter Soldier, Age of Ultron, and Civil War. However, what actually causes the Avengers to split into two teams?
In the comics, the Stamford incident was what forced the government to come up with the Registration Act. In the movie, there will be a different kind of incident, which many suspect will be the bombing of an UN council meeting.
The writers didn't actually reveal what kind of incident it is. However, producer Nate Moore gave the fans a few hints. According to Hit Fix, Crossbones will play a crucial part in it. Which makes us believe that the few scenes from the trailer in which he appears are indeed the ones which provide the grounds for a Civil War.
But the producer went even further, saying that this is a different Brock Rumlow, one who doesn't work for anybody but himself. Apparently, Crossbones now has his own agenda "“ could it be payback for his disfigurement?
However, we shouldn't actually trust the producer entirely "“ he may be sending the fans in the wrong direction when he says that Crossbones has his own agenda. Maybe he has one "“ but is it still just part of a bigger and more evil plan (Zemo anybody?!?)?
