Tenifa is currently serving up to 30 years at the Utah State Prison on 2001 convictions for robbery and aggravated assault. He has been paroled four times through the years, most recently in May 2012, according to parole authorities.

He faces a new charge of object rape, filed in September 2013 in Cache County’s 1st District Court, and was charged last year in federal court with being a felon in possession of ammunition.

The defendant, Siale Angilau, age 25, also had a long criminal history.

Prosecutors only disclosed to the defense a few weeks ago that Tenifa would be a witness. The defense filed motions saying it needed more time to prepare for his testimony and assemble impeaching information, but the court denied the motion.

(Defense Attorney) Langford argued that "to properly defend himself against a potentially devastating witness with highly suspect integrity, credibility and firsthand knowledge," Angilau and his defense team needed time they were not given to prepare.

Perhaps Angilau was surprised by Tenifa's testimony and reacting to the "trial by ambush" strategy of the prosecutors.

Angilau may also have been angry that state prosecutors obtained a guilty plea from him in 2008 in a case in which an associate had fired shots at a U.S. Marshal. Both the prosecutor and a representative of the Marshal's Service recommended no federal charges be filed against him as a result of the incident. But he was charged anyway. In July, 2013, the 10th Circuit rejected his appeal. From the opinion:

The first charges against Defendant arising out of the August 2007 shooting of the marshals were brought in Utah state court in March 2008. He pleaded guilty to obstruction of justice and failure to stop at the command of police. At
his change-of-plea and sentencing hearing in state court, both the prosecutor and a
representative of the United States Marshals Service agreed to recommend against federal charges in connection with the shooting, although the court explained to Defendant that this was merely a recommendation.

Shortly thereafter, in July 2008, Defendant was indicted in the First Federal Case on charges arising from the July 2007 robbery of a 7-Eleven store, which predated (and is apparently unrelated to) the shooting of the marshals.

...For reasons not disclosed by the briefs or the record, the government then changed its mind several times about how to prosecute Defendant for the marshals shooting. In September a second indictment brought two charges against him based on the assault on the marshals (the Second Federal
Case): assaulting the two officers, see id. § 111(a), and using firearms during the
assault, see id. § 924©. But then in January 2009 the government obtained a superseding indictment in the First Federal Case, adding the two charges brought in the Second Federal Case.

Again changing course, that May the government
dismissed without prejudice the two added charges (relating to the marshals shooting) in the First Federal Case and Defendant pleaded guilty to the original charges arising from the 7-Eleven robbery. Three months later the government
dismissed the marshals-related charges in the Second Federal Case, leaving no charges pending against Defendant.

But that was not the end of the government’s attempts to prosecute Defendant for the marshals shooting. Apparently desiring to charge the shooting as part of a broader RICO case against additional defendants, the government filed a second superseding indictment in May 2010 in the case now before us. It included numerous charges against members of the Tongan Crip Gang, a criminal organization to which Defendant is alleged to belong.

As previously noted, four counts name Defendant. The racketeering-conspiracy charge makes no mention of the marshals shooting in the overt acts it sets forth. The other three counts—the assault count, the VICAR count, and the firearm count—arise out of the marshals shooting. (my emphasis)

...Defendant appeals. He argues (1) that the district court should have dismissed the VICAR and firearm counts on the ground that the government, by repeatedly charging and dismissing counts arising from the marshals shooting,
engaged in prosecutorial harassment so severe as to constitute a violation of his due-process rights....

Federal RICO charges are challenging to understand even for many lawyers. Given that he was 25 and had no legal training, I wouldn't be surprised if he was unable to make sense of the Court's explanation and believed the system was riding rough-shod over him. And with the feds trotting out this new witness to bury him, it sounds like he just finally snapped in Court.

In my experience (and that of many other defense lawyers), U.S. Marshals are generally among the more mellow law enforcement agents. They are charged with bringing detained defendants to and from the courtroom, and almost all my clients remark about how friendly and at times even helpful they are (as compared to DEA, ATF, FBI, etc.) But it is kind of odd that this Utah Marshal reportedly kept shooting after the first shot brought the defendant down. One man in the courtroom, Perry Cardwell, whose wife was scheduled to testify against the defendant (pertaining to a 7-11 robbery when he was 14 and she was the clerk) said the Marshal shot about 8 times. The husband certainly has no reason to make stuff up that's favorable to the man his wife was about to testify against.

"Everything was so fast," Cardwell said, adding that he thought he heard eight shots fired.
Angilau then fell to the floor, and Cardwell said the marshal kept firing.

"I thought, when is he going to stop shooting?" Cardwell recalled.

This was the first trial held in Utah's brand new federal courthouse which opened last week. The courthouse has gotten a lot of bad press for being ugly and too austere. I agree -- it looks more like a jail than a courthouse.