BOSTON (AP) — Plucking a couple of faces in baseball caps out of a swarming crowd, the FBI zeroed in on two suspects in the Boston Marathon bombing and shared surveillance-camera images of them with the world Thursday in hopes the public will help hunt them down.

The somewhat blurry but still detailed photos and video depict one young man in a dark cap and another in a white cap worn backward, both wearing backpacks and one walking behind the other on the sidewalk near the finish line as marathoners run by.