Link looks around from his hiding spot - and realises there's just one guard left, now. They're shooting at Elma, but she's darting for cover. And with them focused on her, they aren't looking at what Link's doing.

Well, he's already got this bomb. Might as well use it.

He throws it towards the guard, takes a quick look towards Elma to make sure she's far enough away - and then detonates.