St. Petersburg, Florida -- A grand jurywill take up the case of Trayvon Martin, the 17-year-old boyfatally shot by a neighborhood watch volunteer near Orlando. The grand jury is expected to convene on April 10th.

Meantime, an attorney for Martin's family called on officials Tuesday to arrest 28-year-old George Zimmerman for what he says was "a cold blooded" killing.

"Right now he is free as a jaybird, he's allowed to go and come as he pleases while Trayvon Martin is in a grave," attorney Benjamin Crump told reporters.

Photo Gallery:FL teen killed by neighborhood watch volunteer

Crump also said Martin was on the phone talking with a 16-year- old female friend moments before he was killed on February 26th. During the conversation, Crump says Martin told the girl he was being followed. The two continued talking until a man, presumably Zimmerman confronted Martin.

"She hears Trayvon say, 'Why are you following me?' and that's when she says she hears the other voice say, 'What are you doing around here?' and again Trayvon says, 'Why you following me?'"

The girl has told Crump that's when she believes Martin gets pushed and then the call is cut off. The girl, who Crump is not identifying, says Martin also seemed normal while talking over the phone.

"All this stuff about him being high and stuff is preposterous. It's what Zimmerman wants you to believe so he can justify killing this kid in cold blood," Crump said.

Later this week civil rights activist Al Sharpton is expected to travel to Sanford for an evening town hall meeting to discuss how the case has been handled.

But already celebrities like Spike Lee, Mia Farrow, Michael Moore, Russell Simmons and others have turned to social media to raise awareness of the case, many of them urging people to sign an online petition calling for a Zimmerman to be arrested. The petition, through the website, has drawn more than 500,000 signatures so far.

Photo Gallery:Trayvon Martin photos

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