"It looked like there were strikes being thrown, punches being thrown," Good said.
Later, under cross-examination, he said that it looked like the person on top was straddling the person on bottom in a mixed-martial arts move known as "ground and pound." When defense attorney Mark O'Mara asked him if the person on top was Martin, Good said, "Correct, that's what it looked like." Good also said the person on the bottom yelled for help.
Zimmerman, 29, could get life in prison if convicted of second-degree murder. Zimmerman followed Martin in his truck and called a police dispatch number before he and the teen got into a fight.
Zimmerman has denied the confrontation had anything to do with race, as Martin's family and their supporters have claimed.
Manalo, whose wife had testified earlier in the week, was the first neighbor to step outside and see what happened with his flashlight after he heard a gunshot. He took cellphone photos of a bloodied Zimmerman and Martin's body, and those photos were shown to jurors on Friday. Manalo also described Martin's hands as being under his body.
Manalo said Zimmerman didn't appear shocked and acted calmly. After police officers arrived and handcuffed Zimmerman, the neighborhood watch volunteer asked Manalo to call his wife and tell her what happened.
Manalo started to tell Zimmerman's wife that her husband had been involved in a shooting and was being questioned by police when "he cut me off and said, 'Just tell her I shot someone,'" Manalo said.
Under cross-examination, Manalo said when he asked Zimmerman what happened, the neighborhood watch volunteer told him, "I was defending myself and I shot him."
"From what you could tell at that moment, that seemed completely true?" asked defense attorney Don West.