Yeah I'm thinking small caliber bullet too. Take a look through the hole with a good light, might see a slug embedded? Or just someone with a spike hammer of some sort?? (I'm really trying to restrain myself, want to avoid ranting about what happened to bumpers in the last 30~40 years or so.)
It looks like someone just came by with a power drill and stuck it in the bumper. Damn Posted via the PriusChat mobile app.
Reading this thread makes me think we need a CSI lab with a spare bumper where they have all the suspected weapons lined up and test hit the bumper with each one and compare the tool marks to find the culprit.