A witness has described seeing a naked man chewing on the face of another man on a road in Miami before the attacker was shot dead by police.
Larry Vega said he was riding his bike on Saturday afternoon off the MacArthur Causeway, which connects the centre of Miami with Miami Beach, when he saw the savage attack on the bridge's off-ramp.
He told WSVN-TV in Miami: "The guy was, like, tearing him to pieces with his mouth, so I told him, 'Get off'. The guy just kept eating the other guy away, like, ripping his skin."
The victim was identified by the Miami-Dade County Medical Examiner's office as Rudy Eugene, 31, according to Miami television station WFOR.
Mr Vega flagged down a Miami police officer, who he said repeatedly ordered the attacker to get off the victim. The attacker just picked his head up and growled at the officer, Mr Vega said.
As the attack continued, Mr Vega said the officer shot the attacker, who continued chewing the face of the victim, who was also naked. The officer fired again, killing the attacker.
Miami police have released few details about the attack, other than confirming that there was a fatal officer-involved shooting.
The name of the victim, who was taken to Jackson Memorial Hospital, had not been immediately determined by authorities, said Detective William Moreno. A spokeswoman said the hospital would not be releasing any information about him.
A surveillance video camera from the nearby Miami Herald building captured images of the men's naked legs lying side by side after the shooting.
Mr Vega said the victim appeared gravely injured: "You couldn't really see, it was just blood all over the place."