FBI, DHS warn of possible 'follow-on or retaliatory' attacks in wake of Trump assassination attempt

The Department of Homeland Security and the FBI have issued a bulletin to law enforcement across the country warning them that, in the wake of Saturday's attempted assassination of former President Donald Trump, violent extremists could try to conduct "follow-on or retaliatory" attacks at events over the next few months related to the 2024 presidential election.

The bulletin urged local, state and federal law enforcement -- and their partners -- to remain vigilant and report any suspicious behavior.

"The FBI and DHS remain concerned ... particularly given that individuals in some online communities have threatened, encouraged, or referenced acts of violence in response to the attempted assassination," said the bulletin, issued Monday night as the Republican National Convention got underway in Milwaukee to officially nominate Trump as the Republican Party's candidate for the White House in November.

Shortly after Trump began speaking Saturday at a campaign event in Butler, Pennsylvania, a 20-year-old Pennsylvania man, Thomas Matthew Crooks, opened fire from a nearby rooftop, with a bullet grazing Trump's ear and leaving the former president bloodied.

Though Monday's night's bulletin said federal authorities are still trying to determine exactly what motivated the shooter, the bulletin noted that "the resonance of divisive topics in public discourse" could contribute to the current threat environment.

It also said that "lone actors" or small groups of extremists "likely will continue to view" political rallies and campaign events as "attractive targets."

At the same time, the bulletin suggested that it can be challenging to detect such threats, especially given the "highly personal nature of radicalization and mobilization to violence."

Even before the attempt on Trump's life, federal authorities had observed politically inspired attacks and plots targeting government officials and candidates for office, and observed an array of "disruptive tactics" against election-related targets, including hoax bomb threats, swatting, and letters with white powder sent to election officials and offices, according to the bulletin.

Last year, scores of envelopes containing white powder were sent to Republican lawmakers and officials in at least three states -- Kansas, Tennessee, and Montana -- but the substances were deemed harmless, ABC News reported at the time.

And over the past year, with false claims that President Joe Biden stole the 2020 election from Trump still persisting, authorities have warned that state and local election officials -- and even poll workers themselves -- are increasingly under threat.

"Domestic violent extremists across ideologies are likely to view a wide range of entities directly and indirectly associated with elections as viable targets for violence," and they "could seek to use a range of violent or disruptive tactics against election-related targets," Monday night's bulletin said.

The attack targeting Trump "reinforces our assessment that election-related targets are under a heightened threat of attack or other types of disruptive incidents," the bulletin added.

The bulletin offered some "preliminary" information about Crooks' actions before he opened fire.

It said that on the day of the attack, "prior to arriving at the campaign rally, Crooks purchased 50 rounds of ammunition from a gun and ammunition shop in Bethel Park, Pennsylvania," and that in the months before the attack, he "received several packages, including some marked as possibly containing hazardous material."

Two improvised explosive devices were found in his vehicle, parked near the rally, and another one was found at his home, according to the bulletin.

"Investigation is ongoing regarding possible motive and ideology predicating [his] actions," the bulletin said.

Speaking to reporters at the White House on Monday, Homeland Security Secretary Alejandro Mayorkas said acts of violence like the assassination attempt on Trump "are unacceptable in our country and in our democracy."

"We are in a heightened and very dynamic threat environment," he said, with constant threats targeting both Trump and Biden.

Mayorkas said that at the Republican National Convention, authorities have "steadily increased the implementation of significant physical and technical enhancements," including "miles of anti-scale fencing, screening technology, and tactical support."

He also said his department has deployed agents and officers from Homeland Security Investigations and the Transportation Security Administration to the convention.

In a similar report issued Monday by the Joint Regional Intelligence Center in California, officials offered several statistics showing how violence against public officials is a growing threat.

"The number of federal charges against individuals threatening public officials has risen steadily since 2017," the report said. "Between 2013 and 2016, federal law enforcement agencies initiated an average of 38 threat-related cases annually. The number of cases increased sharply to an average of 62 a year between 2017 and 2022, and continued to grow in 2023 and 2024, according to open source reporting."

At the same time, the report said that communicated threats alone are a "poor predictor" of actual violence, with studies showing that fewer than 10% of individuals who attacked public officials "voiced threats directly to their victims or to law enforcement."

The report suggests that family members, acquaintances and others may be in the best position to detect when someone is potentially moving toward violence.