The prisoner transfer van stopped at a McDonald's north of Houston for a quick breakfast. Cedric Joseph Marks saw an opening.
The mixed martial arts fighter sprang from the van in Conroe, Texas, authorities said in a news conference, shedding some of his clothes and triggering a manhunt.
Marks, 44, has three pending murder charges against him and is "considered extremely dangerous," the Montgomery County Sheriff's Office wrote on Twitter. He was wearing an orange jumpsuit and restraints when he fled. Police found his shirt while on his trail.
It was not immediately clear how Marks escaped. The van held 10 prisoners and two guards, although only Marks escaped, KCEN reported.
Marks had been extradited from Michigan after he was accused of breaking into the Temple, Texas, home of Jenna Scott, his ex-girlfriend, according to KCEN. Scott and her friend Michael Swearingin were found dead in Oklahoma on January 15.