There are many flashing lights from guns being fired and so on. Also, the mystical beings look like they're made of blueish-white light, and they move extremely quickly (whooshing) much of the time, with motion trail effects. There may be more stuff that can be triggers for people who are sensitive to light; I'm not sure.
Some people fall to the ground from halfway down the side of a building (they're lowering themselves down with ropes), but I don't think we're told/shown that they die. I'm not 100% sure, though.
May be a trigger for people scared of ghosts. For me personally, it wasn't, even though I'm terrified of ghosts, because they're not the "standing in your bedroom in the dark looking at you" kind. They look like they're made of something like liquid blueish light, and they only appear in a military setting, mostly in daylight. Nothing like pale little girls in oldfashioned nightgowns. :)