"Why does everybody I save keep dying?"

bro would probably just think it was a coincidence

But superheroes save lots of people
Eventually people would think something's up

superheroes tend to save big amounts of people at once and people in final destination die in most chaotic ways, so there would be mayhem that just seemingly is coincidental

Yes, but superheroes do large saving sprees regularly, so when everyone saved by said superhero dies in a pattern, multiple times, it starts to get suspicious