The Left Overs

Alice woke up one morning, slipped on her clothes, fixed her hair, and headed downstairs. Her parents weren't home but that wasn't odd as they worked early. What was odd though was when she stepped outside, all signs of life were gone. Empty roads and empty buildings. Of course, the first thing alice does, is pull out her phone to message her friends. It won't turn on. Dead? She could've sworn she had charged it last night. What's happening?