Catch his breath? That's the sort of advice Reiner gives others and rarely takes for himself. He'll catch his breath once they're out of combat, not before.

Seeing that Hakkai is holding them off, Reiner gets to his feet and positions the rifle again. He gives Hakkai a word of warning:

"Firing."

Then: BANG. BANG. BANG. BANG.

Two bullets into one kelpie, two into the other.

… But unlike the first kelpie that appeared visibly wounded, these two seem to be—what? Ready for it? Hardier, maybe? Whatever the case, the standard-issue bullets don't appear to do a damn thing.

Reiner curses and unslings the rifle. "Take this," he says, holding it out to Hakkai, "and run back to the headstones. I don't want to catch you in the blast."