It took approximately three minutes for Lukas to do something. During that time, Cary fought and distracted the ghast almost single-handedly.
The ghast was enraged. This fury both made it a threat and far more predictable. Cary, despite not being in his prime physical physique, still used this to his advantage. He wasn't a Hunter for no reason after all.
He did receive some help during the three minutes until Lukas acted, but most of the help didn't change much. Of course, those using ranged weapons continued firing, although a few had begun to run out of arrows and bolts. A few others tried to help in melee combat or through other means such as distracting the ghast or attempting to restrain it.
All of it did little to nothing.