A defendant in a gang-related trial was fatally shot by a U.S. marshal inside of a new federal courthouse in Salt Lake City Monday after he allegedly tried to attack a witness.

Witnesses say that 25-year-old Siale Angilau, a member of a Tongan Crip Gang (TCG), lunged at the witness with a pen or a pencil around 9:30 a.m. He was the last defendant on trial in a series of Tongan Crip-related cases that the U.S. Government began prosecuting back in 2007.

Officials say that he was shot multiple times in the chest. A group of marshals then continued to hold Angilau at gunpoint in the courtroom.

According to The Salt Lake Tribune, Angilau died early Monday afternoon at a local hospital from his wounds .

"During the trial this morning the defendant went after, engaged the witness stand, and when he engaged the witness at the witness stand, he was shot by the U.S. Marshals Service," said FBI spokesman Mark Dressen, according to USA Today. "From what I understand, the defendant may have grabbed a pen or a pencil and charged the witness stand at that time," he said.

No one else was injured.

A spectator said that the marshal fired eight shots at Angilau after he jumped up from the defense table and tried to punch the witness, who was a prison inmate that was testifying about the gang.

Angilau, who was on trial on racketeering charges, has a long criminal history that includes a string of robberies and assaults of local store clerks, in addition to being accused of shooting two U.S. marshals and brandishing a firearm.

After the incident, U.S. District Court Judge Campbell declared a mistrial.

"The court has met with the jury and and observed that most of the jury members are visibly shaken and upset by this episode,'' the judge wrote. "The court finds that this occurrence in the courtroom would so prejudice Mr. Angilau as to deprive him of a fair trial."