A bus driver passing the scene of the Miami face-chewing attack told a 911 operator a naked man was beating another man to a pulp.
On a recording released Friday, the female bus driver urged the operator to send help.
The driver said: "He's going to kill that man, I promise you."
Surveillance video shows 31-year-old Rudy Eugene attack 65-year-old Ronald Poppo alongside a busy highway last Saturday afternoon.
A police officer fatally shot Eugene, who bit into Poppo's face.
Police have not released a motive for the attack on Poppo, who remains hospitalized.
A male 911 caller reported two men fighting, almost knocking a woman off her bicycle.
Another male caller said a man was taking off his clothes and throwing them into the street.
The caller said: "You can't miss him. He's naked."