BOSTON, Mass. (NBC News) -- Surviving Boston Marathon bombing suspect Dzhokhar Tsarnae pleaded not guilty Wednesday as 30 survivors and victims' relatives listened in a Boston courtroom.
Tsarnaev, 19, was arraigned on a 30-count indictment that charges him with using weapons of mass destruction and killing four people. He wore an orange jail jumpsuit and his left hand was bandaged.
Earlier, a small group of Tsarnaev's supporters cheered as a caravan carried him to the courthouse, invoking his nickname as they yelled "Justice for Jahar!" according to the Associated Press.
Security was tight with Department of Homeland Security officers visible and a police boat behind the courthouse. Seventeen officers from the Massachusetts Institute of Technology lined up in uniform outside in apparent tribute to slain colleague Sean Collier.
Everyone injured in the bombing was invited to attend, and 30 were in attendance, the magistrate said.
Before the arraignment, the mother of two brothers maimed in the blast said she would be looking for answers.
"I want to know what happened that day," said Liz Norden, whose sons, J.P. and Paul, each lost a leg in the April 15 explosions near the finish line of the iconic race.
"How can somebody do something to innocent people like that?"
The 3:30 p.m. hearing marked Tsarnaev's first appearance in public since he was hauled bleeding from a boat, where he scrawled anti-American messages while hiding out from police who locked down the Boston area to hunt for him.
His older brother, Tamerlan Tsarnaev, was killed in a shootout with police — capping a bloody escape bid in which they allegedly killed Collier, hijacked a car and hurled pipe bombs from an SUV.
Three people were killed in the bombing and more than 260 wounded, many of whom lost limbs.
Norden's sons told NBC station WHDH that they won't be in the courtroom when Tsarnaev appears, but they understand their mother's need to be present.
"I just feel I can maybe find some answer or a peace of mind by going," she said.
Attorney General Eric Holder has not yet decided whether to seek the death penalty for Tsarnaev, an American citizen who was born in Dagestan.
Investigators say the messages the college student left in the boat gave them insight into why he and his brother planted the bombs.
They included: "The U.S. Government is killing our innocent civilians," "I can't stand to see such evil go unpunished," and "We Muslims are one body, you hurt one you hurt us all."