Salt Lake City Fire spokesman Jasen Asay would not comment about the advisory on Friday morning, but stressed that the department is functioning as normal.
A copy of the memo, which was obtained by Fox 13 News, advised employees that there have been "several credible threats to law enforcement officers."
The memo further explained that "threats indicate law enforcement can expect shootings aimed at the vehicles and homes of police officers who live in Glendale," according to the television station.
Police and fire officials were advised to limit their exposure in areas where gang members are known to frequent, including Riverside Park, Poplar Grove and Jordan Park.
"Gang members will take any target of opportunity, including scoping out the courts for attorneys walking to and from while the case is still hot," the memo said. "Informants have gone so far as to mention specific gang officers in the RICO case."
According to a federal court transcript, a prosecution witness, Vaiola Mataele Tenifa, had been testifying about how TCG operates, and how they recruit young members before he was attacked.
After being asked how younger people get noticed by older TCG members, Tenifa began telling the jury that one way is by "striking up on walls" referring to spray-painting graffiti just before Angilau rushed toward the witness stand and shots were fired.
Witnesses who were in the courtroom said it appeared Angilau was trying to punch Tenifa when the shooting began.
Angilau was among 17 TCG members and associates indicted on racketeering charges in May 2010. Federal prosecutors allege the gang has committed murders, robberies and assault to expand its operation in the Salt Lake Valley over two decades.
Of the 16 other TCG members indicted in the racketeering case, six defendants took plea deals, six were convicted in a September 2011 trial, two were acquitted and charged were dismissed again two in 2012.
To bring charges under the Racketeer Influenced and Corrupt Organizations (RICO) Act case, prosecutorshad to show that the Tongan Crip Gang actually exists, and that members of the gang committed crimes to enhance their standing in the gang and expand the gang's operations.
Court documents allege Angilau was involved in an incident in which bullets were fired at two U.S. marshals in August 2007, for which he had been serving time at the Utah State Prison. The racketeering case also linked Angilau to several violence convenience store robberies between 2002 and 2007.
Tenifa, who is serving up to 30 years at the Utah State Prison on 2001 convictions for robbery and aggravated assault, was not injured in the attack.