"I've called this nothing short of an assassination," Nutter said on MSNBC. "This individual Zimmerman followed Trayvon for some period of time. Trayvon was not a threat to him.
"Clearly Zimmerman was told not to continue any kind of pursuit. In my view at least . . . he tracked [Trayvon] down. He followed him and then shot and killed him. It's incomprehensible to me why an individual would do something like this, unless he had something either in his heart or on his mind."
Public condemnation of how police in Florida have handled the case - they have not arrested Zimmerman - has been unrelenting. Critics have maintained that Martin's race - African American - played a factor in his shooting. Zimmerman's racial background is mixed, with a Hispanic mother and a white father.
The uprising over the police handling of the case has forced the temporary resignation of the police chief in Sanford, the small town where the shooting occurred. The U.S. Justice department has launched an investigation, in part to determine if a hate crime was committed.
On Feb. 26, Martin had been at a 7-Eleven and was walking back to his father's home in a gated community to watch a basketball game when Zimmerman started following him and ultimately shot him. Zimmerman has contended that he shot the teenager in self-defense, and was released by police after questioning.
Martin had been carrying a bag of Skittles candy and a can of ice tea.
The shooting has drawn international attention to Florida's so-called Stand Your Ground law. It allows someone to "stand his or her ground and meet force with force, including deadly force," if that person feels it is neccessary to prevent death or bodily harm.
Some of Zimmerman's friends have come to his defense saying he is not a racist and was prompted to pull the trigger because he feared for his life.
On MSNBC, Nutter said Zimmerman "based on all information, clearly should be in police custody. That's the first failing in the aftermath of his actions."
"There was a young boy who was minding his business, a young African-American male . . . good kid based on everything that we know, and this guy on his own shoots him down with no logic, no reason, and no response from the law enforcement officials down in Florida."
"People will not rest until there is some justice on behalf of that young man, Trayvon Martin, and many, many other young people across the United States of America, especially African American males," Nutter said.
Contact Darran Simon at 856-779-3829 firstname.lastname@example.org or follow on Twitter @darransimon.