Puente desde lo profundo

If Bridge from Below isn't in your graveyard immediately before a creature dies, its abilities won't trigger at all. If Bridge from Below isn't still in your graveyard as its first ability resolves, you won't create a token.

If a nontoken creature you control and a creature an opponent controls die at the same time, you choose the order in which Bridge from Below's triggered abilities resolve. You can create a token before you exile Bridge from Below.

Neither ability cares who controlled the creature that died, only which graveyard it was put into. This means that if an opponent controls a creature you own, its death causes Bridge from Below's first ability to trigger, not its second.

While Bridge from Below is on the battlefield, it has no effect. It does something only if it's in a graveyard. Yes, this is a bit weird.