They were crawling on the wall. Didn't move fast enough, so they aren't alive anymore. Well they flew a little on the wall, but didn't fly away.

Stupid fly, slow because they are inside, probably dying.

Maybe there was only one fly. If so, maybe the camera won't record anything while sleeping. Except, sometimes it records more then one thing at a time, so only one fly, wouldn't explain it.

Should have put them in the hallway or outside though. Killing flies is probably bad for your karma. And God said not to kill, that includes bugs.

Except, the God might have been an Alien that said that.

In some places people use a broom so they don't step on bugs. I bet they still kill bugs sometimes, without knowing. Like when one crawls in their mouth, and they swallow it. When sleeping of course. If I had a pet lizard, they'd eat the flies.