A federal marshal shot and killed the defendant in a gang trial in Salt Lake City on Monday after he tried to attack a witness, authorities said.
The defendant, Siale Angilau, was being prosecuted in a racketeering investigation into the Tongan Crip gang.
Sources told NBC News that the defendant appeared to grab an object and started toward the witness in "an aggressive, threatening manner," and then the marshal fired multiple rounds.
Angilau was shot in the chest and then taken from the courthouse in an ambulance, according to the U.S,. Attorney's office in Salt Lake.
He later died of his wounds, federal officials said.
Several defendants in the case were convicted in 2011. The lead defendant, Eric Kamahele, is serving a 30-year federal prison sentence. Angilau’s case was being tried separately.