I was stuck on the last one for about 30 minutes last night figured out just running up to the marker stops the enemies from following you then I just kept punching it till it broke apart. It actually shows the marker breaking as you go. The first 2 visions I beat by just dumb luck I guess.
I'm not sure if you have to kill a certain number of shadows or not, but I just went up to the marker and started unloading and every 10 shots or so it started cracking and eventually broke after 30 rounds with a weak gun. There's also a marker in the regular room with Issac, i'm not sure if he can shoot it also and speed things up though
Shoot the marker. I died a couple times figuring it out, the trick for me was to stand next to the sofa right up against the marker. The enemies stopped moving, and i was able to unload into it which cracked it and eventually broke it. Perhaps the enemies stopping was a glitch.