Trayvon Martin had no arrest record or disciplinary action for violence as a student in North Miami's Krop High School.
On Monday Lee, seeking to head off racial unrest, tried to reassure the public that his department was doing all it could to reach a fair conclusion, as some in the crowd heckled him saying "a little black boy is dead."
Lee's department said it plans on passing its investigation over to the state's attorney office to determine whether or not to press charges against Zimmerman.
Trayvon Martin's parents described him as the kind of son who even at 17, allowed his parents to kiss him publicly.
"That was my baby, my youngest son," mother Sybrina Fulton told ABC News in an interview in Miami. "He meant a lot to me, I don't think the police department really understands that…I need justice for my family, I just want justice for my son."
Fulton is incensed that Zimmerman left his car despite being urged against it by dispatchers to stay put.
"My son didn't do anything he was walking home from the store. Why would the neighborhood watch guy would have a weapon?...It's just crazy.You are supposed to watch the neighborhood, not take the law into your own hands."
ABC News' Matthew Rosenbaum contributed to this report.