Trayvon Martin shooter George Zimmerman appeared in a Florida courtroom shortly after 1:30 p.m. He entered the courtroom in handcuffs.

Flanked by a police officer and his lawyer, Mark O'Mara, Zimmerman acknowledged the second-degree murder charge against him. He spoke only briefly, saying "Yes, sir" twice, and did not enter a plea.

The judge agreed there was probable cause to proceed, and set for a formal arraignment on May 29, at 1:30 p.m. ET. O'Mara said Zimmerman would plead not guilty.

Zimmerman is being held in protective custody without bail in Seminole County Jail. O'Mara did not ask the judge to set a bond, but asked for the case file to be sealed. The prosecutors agreed to the request.