to be an explosion of some sort or a big blaze. it has six men in front of the flame as if they may blown up something and not feel bad about it. behind the men and in the flames appears to be an old car of some sort. it probably had the six men in the vehicle or someone died in it. it could also be that they are above the movie title gangster squad and may be the squad in the movie.
the poster designer is probably trying to get everyone's attention of the three men with weapons and the flames between them. to also make people know that 