Using the word "murder" in "killer explosion"

I saw a post today on social media

"78 people were killed by the explosion in Lebanon"

And I commented "since you used the word "killer" rather than "died", can we assume it’s a murder?"

I got hate comments suddenly and got confused, I know it’s common to use killer in storms, earthquakes and such but can we also use the word murder?
Does using the word killer really is correct?

I’m confused, thanks for the answers