Luigi Mangione, Chelsea Manning. Photo:

Yuki Iwamura/Bloomberg via Getty; Chelsea Manning/Instagram

Famed whistleblower Chelsea Manning was one of more than 100 people who packed a Manhattan courtroom on Friday, Feb. 21, to support Luigi Mangione ahead of the accused murderer’s hearing.

Manning, who served jail time for leaking military cables to WikiLeaks before having her sentence commuted, told PEOPLE she had arrived at the courthouse at about 8:15 a.m., ahead of Mangione’s scheduled 2:15 p.m. appearance to answer state charges that he murdered Brian Thompson, the CEO of UnitedHealthcare.

“I am here exercising my Sixth Amendment right,” Manning tells PEOPLE in a courthouse interview. “I am a member of the N.Y.C. public here to witness our court proceedings.”

The Sixth Amendment to the Constitution guarantees, among other things, the right to a speedy and public trial.

Manning was one of more than 100 supporters who showed up to the Manhattan Supreme Court to support Mangione. Supporters have also raised more than half a million dollars for his legal defense and put up a large billboard in lower Manhattan depicting Mangione as a saint.

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The courthouse crowd erupted in applause as Mangione’s attorney, Karen Friedman Agnifilo, arrived ahead of the hearing.

If convicted of the state murder charges against him, Mangione could face life in prison. He also faces federal murder charges in Manhattan that could land him the death penalty if convicted.