Who killed the critters?

When I returned to my apartment after a weekend in the Bay, I started at the sight of various winged varmints lying in their deathly glory on my bathroom floor and in the tub. I had just cleaned the bathroom a few days prior!

It was horrifying enough that these cretins had found their way in, but what could have been the cause of their simultaneous moribund condition? The temperature is in no way extreme, and they had plenty of light and air.

Is there some toxin that annihilated them and is now slowly eating away at my innards?

Or was it the lingering stench of my feces that slaughtered their ambition to live?