By Slanted Light

You said you saw from your window. Were they below the window? Birds can fly headlong into windows and frequently with such force that they break necks. They might also bounce back a bit so they may be a little way off the window itself.

I can't actually see heads, though. Are the heads still on? If ripped off, then I would say sparrowhawk, but I don't know why it would abandon two good prey items.

If it was trichomoniasis - a common bird respiratory disease often leading to death - there would be swelling around the
throat. But normally you see them wandering around in a daze before it get to death, so you would have noticed these two, I expect.

So sorry for your rotten run of days! :((((