On mission where I have to take photographs of four people

[zerstemvale]

For this mission I have to kill 4 people for Sander Cohen. I've killed 3 of them and taken their pictures. I brought them all back to the atrium and posted the pictures. Then splicers started coming out everywhere and I killed 12 I think then they stopped spawning. Now I checked the map and the mission says I have to go to 'rapture records' and kill 'silas cobb' and get his picture for Cohen. I am wandering around and around in the atrium and there is no way out. The doors are all closed, even the one leading back to poseidon plaza, where rapture records is. This feels broken to me and I think I have to reload an earlier game in order try this again, hopefully successfully this time. Unless if there's some way I can spawn his body with a console command so I can take a picture of it; I think I am screwed.

Edit: I went back and I learned it doesn't have to do with any of the 4 npc's you have to kill but with the part where you must kill cohen's splicers. I encountered the same bug again and instead of reloading, I 'ran into the poseidon plaza' door for a few seconds and 2-3 more splicers appeared, seemingly behind me and after i killed them, it wasn't bugged anymore and I could go on.