This just happened to me yesterday (May 2024) but my head was close to the explosion and I'm lucky that the only effect is a ringing in my ears. I took the battery out of off-season storage where it was temp controlled and hooked to a charger. The battery is for my boat lift. It didn't work. A few days later (yesterday) I tried again and when I turned the key on the boat lift it was like a bomb went off. I felt the concussion and the neighbors all came out. Short story after speaking with someone from the boat lift company: he said "there wasn't enough water in it". I understand batteries now are sealed but mine was a green interstate battery like yours and had removable caps (which exploded upward). Anyone who has a deep cycle marine battery should make sure they understand if they need to monitor the (distilled) water levels in the battery. I was saved by the fact that I was in a squat position to get the key turned and the battery was above my head and exploded upward.

I'm assuming having a well ventilated space could reduce this? In my boat my batteries are in tight compartment. For some reason I have always charged my batteries with a fan blowing into the compartment. After seeing this, I'll will definitely continue doing this!