Trayvon Martin's father says he hasn't yet had the chance to properly grieve for his 17-year-old son, amid questions about how a boy remembered as sweet and "mild-mannered" could end up shot to death by a neighbourhood watch captain.

"We're trying to get some sort of answer, some sort of closure," Tracy Martin, the Florida youth's father, told the CBC's Mark Kelley on Connect with Mark Kelley, in an interview that aired Wednesday night.

Asked how he felt in his heart about neighbourhood watchman George Zimmerman, who allegedly gunned down Trayvon last month while the unarmed youth was walking home from a store, Martin was unequivocal.

"I really don't have no thoughts on him," Martin told Kelley from Washington. "George Zimmerman murdered my son. Ask yourself as a father, how would you feel about the individual that murdered your son?"

Martin said his son was a polite young man who answered respectfully to elders with "ma'am" or "sir."

"I would call Trayvon over in front of his friends just to joke with him, and I would tell him to give me a kiss in front of his friends," Martin said. "And he didn't feel like it was robbery for him to give his dad a kiss. That's the type of person he was."