Boa was the one that stopped things. Not Candy; Candy would have squeezed the life out of him and kicked his body out of the glyph. It certainly wasn't the gun; the feathersteel spell would have held up to that. No, Boa stopped him because he didn't deserve this in her mind.
There was a cry of loss as Candy fought for control of her mind, and a whimper of pain and sorrow as Boa won. The light dissolved, and the glyph steadily descended toward a hill. She reached out for Jack out of instinct, trying to duck his head down.