Board Game Arena

How does the vampire costume work when I would buy High Altitude Bombing (All monsters, including you, lose 3 hearts)? The description of the Vampire card is
At the end of each Monster's turn, if you made another Monster lose at least 1 heart, gain 1 heart.
If I make 4 other monsters lose hearts, do I gain 4 hearts at the end of my turn?

Not getting an answer, I decided to go ahead and see how it worked out. All 4 other monsters lost 3 hearts, as well as myself, and at the end I gained only 1 heart back.

I think that's the only reasonable interpretation, equivalent to "if you made at least one other Monster lose at least 1 heart".