The grand jury had been scheduled to meet Tuesday.
Corey said in a statement that the decision should not be considered a factor in determining whether charges will be filed against George Zimmerman, the neighborhood watch volunteer who fatally shooting the unarmed Martin.
The decision on charges now rests solely with Corey, who took over the case last month after the prosecutor who normally handles cases out of Sanford recused himself.
The 17-year-old was killed Feb. 26 during a confrontation with Zimmerman in a gated community in Sanford, Fla. The shooting led to protests across the nation and spurred a debate about race and the laws of self-defense.
Martin was black, while Zimmerman's father is white and his mother is Hispanic. Zimmerman has claimed self-defense, and Florida's self-defense law gives wide leeway to use deadly force and eliminates a person's duty to retreat in the face of danger.
A police report notes George Zimmerman had blood on his nose and the back of his head. But in a surveillance video, obtained exclusively by ABC News, shows Zimmerman from inside the Sanford police department just after the shooting. Zimmerman's shirt and jacket appear unstained and there is no visible sign of blood on his face.
Zimmerman has been in hiding since the fatal shooting.
A large rally and march will be held on Monday in downtown Los Angeles. Crowds are expected to gather at about 4 p.m. at Pershing Square and then march to the steps of City Hall at 6 p.m.
The Associated Press contributed to this report.