Doug Stanglin, Kevin Johnson and Michael Winter

USA TODAY

A U.S. marshal shot and killed a Pacific Islander gang member Monday when the defendant tried to attack a witness with a pen inside the new federal courthouse in Salt Lake City.

Siale Angilau, 25, a member of the Tongan Crip Gang, was shot several times in the chest about 9:25 a.m. MT after charging the witness in an "aggressive, threatening manner," the FBI said. He died several hours later later at a hospital.

The witness, a Utah prison inmate, was testifying about the gang and how it worked.

"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. "From what I understand, the defendant may have grabbed a pen or a pencil and charged the witness stand at that time."

Angilau was on trial on racketeering charges in the courtroom of U.S. District Court Judge Tena Campbell. Along with a string of robberies and assaults of local store clerks, the 6-foot-3, 260-pound Angilau was also accused of shooting two U.S. marshals in 2007 and brandishing a firearm.

He had been in Utah state prison from September 2007 until being handed over to the U.S. Marshals Service on Friday after the jury had been selected, the Utah Department of Corrections said. He was not restrained in the courtroom.

A spectator told the Salt Lake Tribune that the marshal fired eight shots after Angilau jumped up from the defense table, charged the witness stand and tried to punch the witness, who was wearing a prison jump suit.

The witness was 31-year-old Vaiola Mataele Tenifa, his attorney, Steven Killpack, told the newspaper. He is serving up to 30 years at the Utah State Prison on 2001 convictions for robbery and aggravated assault.

The shooting prompted Campbell to declare a mistrial. She said in a brief order that U.S. marshals had continued to hold Angilau at gunpoint near the jury box while jurors were still in the courtroom.

"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."

Angilau's lawyer, Michael Langford, was not immediately available for comment. His office said the lawyer was "a bit shaken up but okay.''

The federal courthouse, which opened last week with upgraded security, was placed on lockdown.

The Angilau case was the last in a series of Tongan Crip-related trials that have been going on since 2007.

In 2011, a jury convicted six members of the gang for robbery, assault and use of firearms during crimes of violence committed in support of an ongoing criminal organization. Five others agreed to plea deals, and two were acquitted.

The newspaper says some jurors at the time feared retaliation from gang members and wanted assurances from the judge that they would be safe. A note from a juror asking for such assurances nearly caused a mistrial in the case, the DeseretNewsreported.

Contributing: Donna Leinwand Leger; Associated Press