 -- The U.S. Department of Justice's National Gang Intelligence Center has issued a bulletin to law enforcement agencies nationwide, suggesting that the general anger towards police could now be morphing into an organized effort to target both uniformed and plain-clothes officers -- especially by street gangs.

The bulletin was issued on July 15, just two days before the ambush of police and sheriffs deputies in Baton Rouge, Louisiana, on Sunday.

"Gang-related threats and attacks on LEOs [law enforcement officers] have been reported in multiple jurisdictions since the Dallas shootings, and suggest that individuals and gang members may be targeting LEOs for retaliatory violence," the bulletin reads. "Gang members have also issued multiple threats of violence towards LEOs via social media following the Dallas shootings and the officer-involved shootings in Louisiana and Minnesota."

The bulletin cites the shooting deaths of black men by police in suburban St. Paul, Minnesota, and Baton Rouge, and references the deadly sniper attack on police in Dallas. Other highlights in the bulletin include:

-In July 2016, a high-ranking member of the Four Corner Hustlers street gang in Chicago expressed a serious desire to kill a federal law enforcement agent, reasoning that the murder of a federal agent would resonate louder than the death of a local police officer. -According to July 2016 FBI source reporting, United Blood Nation (UBN) leadership is encouraging violence against law enforcement, by promising elevated status to members who initiate violence against police. -Some Black extremist groups are reportedly applauding the death of the five Dallas police officers and are encouraging gangs nationwide to unite and attack law enforcement, according to uncorroborated July 2016 open source reporting.

ABC News law enforcement contributor Steve Gomez, who worked gangs in South-Central Los Angeles first as an LAPD cop and then as an FBI agent, said the bulletin and the threats it details mark a return to the nightmare of the late 1980s and early 1990s.

At that time, the only thing that unified Los Angeles' infamous street gangs was their hatred of law enforcement, and it was common for law enforcement to face sniper fire as they patrolled or responded to calls. The situation deteriorated dramatically, Gomez said, after the Rodney King verdict and 1992 riots.

"If the movement to target and assassinate cops expands past lone wolves (as we have thus far seen in Dallas, Baton Rouge, and other cities), and mobilizes violent gang members nationwide," Gomez said, "the effect could be overwhelming."

In response to the killings of police officers in Dallas and Baton Rouge, many police departments around the nation ordered heightened security for police facilities and directed that cops patrol only in pairs. In Los Angeles, where police already patrol in pairs, chief Charlie Beck on Sunday went even farther by ordering the specialty Metro Division to serve as on-site security for patrol cars responding to calls and directing the LAPD's force of helicopters to monitor black-and-whites and search for possible snipers.