2020 X5 completely dead. Any ideas?

Everything seemed fine and dandy. We get in the car like normal, my husband is putting in his PIN to set the profile, he says it’s hot and he should started the car beforehand, I say well let’s turn it on, so I press the start button and everything died. Literally everything. It made a small pop sound and now everything is gone. Ive called roadside assistance but any idea what this might be? Hoping just the battery but it didn’t give us any warning signs and the fact that nothing works is concerning.