Glissa and Explosives

[MSC]

When I have a Glissa, the Traitor and a Engineered Explosives with 3 Counters on the Board and my Opponent also has a CC3-Creature (lets say two Knight of the Reliquary).
What happens when I activate the Explosives and all three Creatures die? Does Glissa still trigger while going to the Graveyard and I get the Explosives back?

MFG MSC

[luma]

If Glissa and an opponent's creature die at the same time, Glissa's ability will trigger and you will get your EE back. This happens because leaves-the-battlefield triggers (including "put into a graveyard") trigger based on the situation just before the event (Glissa is still on the battlefield with that ability, then an opponent's creature dies), not after.