had something very similar happen to my MIL's car. Lights, radio and such would work. Try to start is and nothing, not even clickity click.

Came over, put my meter on the battery, read 12.8ish. had her turn on the head lights and zoom, below 10v. One new battery later we were good to go. Seen this one before in my clunker years, so I always do an impromptu load test like that when I see similar symptoms, bet you will too now.