A criminal defendant standing trial in Utah’s new federal courthouse was fatally shot by law enforcement Monday after he allegedly tried to attack a cooperating witness.

A deputy U.S. marshal shot defendant Siale Angilau after he “rushed a witness on the witness stand in an aggressive, threatening manner,” the FBI said in a statement. Angilau was shot in the chest and died after being transported to a local hospital. The FBI said no one else was harmed.