(CNN) Usaamah Rahim, who was fatally shot after waving a military knife at law enforcement officers in Boston, was originally plotting to behead Pamela Geller, an activist and conservative blogger, law enforcement sources told CNN on Wednesday.

But Rahim, a 26-year-old security guard who officials believe was radicalized by ISIS and other extremists, decided instead to target the "boys in blue," a reference to police, according to court documents.

"I can't wait that long," he said of the original beheading plan, according to an FBI affidavit filed in federal court in Boston

Geller drew national attention last month after an off-duty police officer working security thwarted an attack at her organization's contest for Prophet Mohammed drawings in Garland, Texas. She's president of the American Freedom Defense Initiative, which includes subsidiary programs Stop Islamization of America and Stop Islamization of Nations.

"They targeted me for violating Sharia blasphemy laws. They mean to kill everyone who doesn't do their bidding and abide by their law voluntarily," Geller told CNN's Erin Burnett after learning of the alleged plot.

"This is a showdown for American freedom. Will we stand against this savagery or bow down to them and silence ourselves?"

Geller said that she's had an "army of security" since last month's Texas incident.

"This is what is required just to show a cartoon in America, 2015," she said. "It's striking. It's devastating, and people need to understand what's at stake. I mean, if we surrender on this point, what will we surrender next?"

'The easiest target'

About two hours before Rahim's confrontation Tuesday with officers on a Boston street, he allegedly told an associate he was "going to ... go after them, those boys in blue. 'Cause ... it's the easiest target," the documents say.

Rahim's alleged associate, David Wright, 25, appeared in U.S. District Court in Boston to face a charge of obstructing a federal investigation by destroying electronic evidence on Rahim's smartphone. A detention hearing was scheduled for June 19 after prosecutors said he was a flight risk.

Wright allegedly attempted to destroy Rahim's cell phone and conceal evidence of their plans, according to the documents. Wright faces a maximum penalty of five years in prison if convicted.

Rahim purchased three military fighting knives with blades longer than 8 inches on Amazon.com, the court documents said.

"I just got myself a nice little tool," Rahim allegedly told his associate, according to the court documents. "You know it's good for carving wood and ... carving sculptures."

In a recorded conversation, the two men are then heard laughing. They apparently share some history.

Under the alias "Abu Sufyaan," Rahim thanked his nephew, "Dawud Sharif Abdul-Khaliq," an alias of Wright, for witnessing his wedding, according to a 2013 Facebook post

Wright's attorney called for caution.

"I would urge the government, the FBI and law enforcement, in investigating this case and related cases, to be as transparent as possible, and in enforcing the law, to abide by the law," Jessica Hedges told reporters. "We have serious concerns about that already."

24-hour surveillance

Boston Police Commissioner William Evans said surveillance video shows four or five officers approach Rahim without their weapons drawn. The officers backtrack as he comes after them and gets "close enough to cause imminent harm." They eventually draw their weapons and open fire.

"We never anticipated what his reaction would be and that he would pull out ... a military knife and approach the officers," Evans said.

Police released this image of a knife Usaama Rahim allegedly waved at officers before being fatally shot.

Anti-terrorism authorities had Rahim under 24-hour surveillance, said Vincent B. Lisi, FBI special agent in charge.

Rahim was a subject of a terror investigation involving suspected Islamist extremists, law enforcement sources said.

"We believe he was a threat," Evans said. "He was someone we were watching for quite some time."

The FBI noted a recent change in Rahim's behavior, including social media threats against police, which prompted agents to try to approach him, according to an official.

Shooting video

Authorities showed the surveillance video of the incident during an unusual meeting with religious and civil rights leaders in an attempt to allay community concerns about the shooting.

Rahim was not on the phone at the time of the shooting and was not shot in the back, as had been reported by a relative, according to clergy and civic leaders who met with authorities earlier Wednesday.

"What the video does reveal to us very clearly is that the individual was not on the cell phone, the individual was not shot in the back and that the information reported by others that that was the case was inaccurate," Darnell Williams, president and chief executive of the Urban League of Eastern Massachusetts, said at a news conference with the police commissioner and others.

Rahim's brother has posted on social media that the suspect was on the phone with their father and was shot three times in the back during the confrontation with police.

Williams said prosecutors want Rahim's family to see the video before showing it to the public.

The religious and civic leaders said Rahim appeared to be shot three times -- in the shoulder, abdomen and chest. Police had earlier reported that he was struck two times.

Imam Abdullah Faaruuq, speaking for the Muslim community, said the video was inconclusive.

"I don't think that he was shot in the back. ... However we couldn't see clearly at all," he said.

He added, "We can't say what happened. We weren't there. We do see a very vague video that is not clear as to what transpired. It wasn't at a bus stop. He wasn't shot in the back and there is not detail enough on the video to tell us exactly what happened."

A third associate

The FBI-led task force had been watching Rahim and two associates also believed to be radicalized, according to a law enforcement official. Rahim had been monitored for at least a couple of years. Investigators were talking to the associates, and various locations in Massachusetts and Rhode Island were being searched, officials said.

The Rhode Island raid was connected to a third person believed to be associated with Wright and Usaamah Rahim, according to two federal law enforcement sources. The third person was connected by more than just an "Internet relationship," one law enforcement source said. The sources did not provide a name for the individual they were investigating.

The FBI is still investigating whether more people are connected with the three.