Boston terrorism suspect
Law enforcement officials are gathered on a residential street in Everett, Massachusetts June 2, 2015 in connection to a man shot dead by law enforcement in Boston after coming at them with a large knife when they tried to question him as part of a terrorism-related investigation, authorities said. The 26-year-old man, identified as Usaamah Rahim, brandished a knife and advanced on officers working with the Joint Terrorism Task Force who initially tried to retreat before opening fire, Boston Police Superintendent William Evans told reporters.Reuters/Brian Snyder

The Isis-inspired terrorism suspect who was fatally shot by members of the Joint Terrorism Task Force in Roslindale, Massachusetts on 2 June planned to behead a police officer, according to an affidavit filed by FBI on 3 June.

Usaama Rahim allegedly planned to murder someone outside of Massachusetts but changed his plans early on Tuesday (2 June). According to the Boston Globe, around 5am EST Rahim allegedly told his co-conspirator David Wright: "I'm just going to — ah — go after them, those boys in blue. Cause, ah, it's the easiest target and, ah, the most common is the easiest for me."

Just two hours later the 26-year-old attacked law enforcement with a large, military-style knife. Rahim was fatally shot by members of the Joint Terrorism Task Force in a CVS parking lot after he refused to drop his weapon, the New York Post reported.

Boston Police Commissioner William Evans told reporters the suspect had been under 24-hour surveillance. Evans said that the members of the task force wanted to question Rahim when he lunged at them with the knife.

Wright, from neighbouring Everett, Massachusetts, was later arrested by police following the attack.

The affidavit filed by the federal agents stated the two men were being investigated for several federal criminal offences, "including terrorism offences". According to the Globe, the investigation found that Rahim was "planning to engage in a violent attack in the United States".

Plot hatched in Rhode Island

The two suspects met with a third individual in Rhode Island on 31 May, where Rahim allegedly told Wright his plan. Wright waived his right to remain silent and told investigators that he had agreed with Rahim's plan and supported it, the affidavit said.

Rahim was shot three times by police, once in the torso and again in the abdomen. He was pronounced dead at Brigham and Women's Hospital. Following the shooting, Rahim's family claimed he had been on his way to work when Boston Police shot him three times in the back.

However, on Wednesday police convened with several community leaders, included leaders of the Muslim community, to show them surveillance footage of the incident. According to Darnell Williams, who heads the Urban League of Eastern Massachusetts, the video "150%" corroborated the police's version of the events.

Meanwhile, Boston Imam Abdullah Faaruuq said that the footage was "vague" but that it did appear Rahim was not obeying the officer's commands. He told reporters: "We're not satisfied until [the case is] fully vetted".

NBC News reported that a senior official said they were investigating whether Rahim had become radicalised through Isis-inspired social media messages. Congressman Michael McCaul, the chair of the House Homeland Security Committee, said on Wednesday that Rahim was spreading Isis propaganda.