**Spoilers**
They were so many of them in the church group with excellent stealth skills, since they already snuck in , why not just give Grace the cure themselves?. And if they were afraid of being stopped, they were already armed and they could've just pulled their guns and tie up the rest of the family in the living room.
Lol you can say this about most movies but yeah, they're dumb. Plus the movie would be 5 min long if they just walked in and held the family at gunpoint while giving her the medicine.
shareAlso at one point they are shown sneaking in and trying to give her the medicine themselves, they turn around and the husband is there so they sneak out instead of just continuing. That's right before they kill him by accident. One person could've just held him while others give her the medicine. Instead they leave lol like NOPE no way we can do it now with 1 old guy sitting here, ABORT. Lmao
shareThey were armed indeed, but they had no guns other than the one they took from Travis -who found it in the garage/barn when taking the tarp off the half-brother's motorcycle, after the invaders had already killed some family members already. So they didn't have any guns when they first broke in, not even when the proverbial sheit hit the fan with the father's death.
And I reckon the plan was indeed to tie up any family member who stood in their way, not killing them. That's why they actually tied one of the brothers and dragged him outside instead of killing him imediately, and also the reason why they were wearing masks. Obviously, the plan was poor and they were amateurs, so chaos ensued.