It was closing time at the Little Caesars restaurant in Holly Hill, Florida. An employee of the pizza chain, Heriberto Feliciano, 28, had just finished checking the security system and was locking up the store for the night.

Before he knew what was happening, he found himself facing a crazed man wearing a clown mask, armed with a wooden post. The man proceeded to land several blows on Feliciano, but the post eventually snapped in two. The assailant then pulled out a pair of...