Feds Urge Vigilance Over Another 'Anti-Islam' Event

The “Freedom of Speech Rally II” is scheduled for Friday.

The FBI, Phoenix Police Department and other law enforcement partners will have a stepped-up presence at the event, authorities told ABC News.

Extremists inside the United States “remain largely unconnected to each other, and their behaviors are often highly individualized, impeding our ability to predict their reactions with a great deal of confidence,” the FBI warned in its bulletin.

The FBI pointed out that Tweets or texts can escalate into something far more dangerous, citing one Twitter user who posted a message online saying, “May Allah send one of his soldiers to Phoenix ameen.”

“Although the most frequent reaction among U.S.-based violent extremists is discussion and verbal disapproval via online communication platforms, the [May 3] shooting in Garland [Texas] illustrates the unpredictable nature of violent extremists and the potential for a single event to generate violence,” the FBI noted in its bulletin.

In addition, the bulletin raises the possibility that technologically savvy extremists could launch cyber-attacks against people or organizations perceived to be defaming Islam.

Like the Texas incident -- during which two alleged extremists were killed by police providing security at that event -- the Phoenix event is set to feature what it calls a “Muhammad Cartoon Contest.”

About 3,700 people were invited online to the Phoenix event, and at least 315 had confirmed their attendance by the time the FBI issued its bulletin Thursday.