By Scott Malone and Elizabeth Barber

BOSTON (Reuters) - The family of a Boston man shot and killed by police after officers attempted to question him in connection with a terrorism investigation said on Thursday they had seen no sign that Usamaah Abdullah Rahim had developed radical views.

Speaking to reporters near the parking lot where Rahim was shot by law enforcement officers who say he confronted them with a large knife, Rahim's family disputed the claim that he had been a follower of Islamic State militants.

Federal investigators, who had Rahim under 24-hour surveillance, said in court papers on Thursday that wire-tapped phone conversations suggested the 26-year-old security guard had planned to try behead police in Boston, a mode of execution also used by Islamic State militants in Iraq and Syria.

"If it wasn't for him being Muslim we wouldn't be hearing terrorism, we wouldn't be hearing ISIS," said a woman who gave her name only as Karen and said she was Rahim's aunt.

Standing with Rahim's mother, three brothers and wife, a lawyer representing the family said Rahim's death had been a shock.

"They have lost a loved one. This loved one is accused of terrible things," said the lawyer, Ronald Sullivan. "The family did not see any signs of radicalization."

Asked if the family denied that Rahim had extremist views, Sullivan said, "We simply don't have any evidence one way or the other."

The family spoke a day after Rahim's nephew, David Wright, was charged with conspiracy to obstruct justice. An FBI affidavit said Wright spoke with Rahim and as-yet-unidentified third person about Rahim's plans, first to travel out of state to kill someone and later to behead police.

A prominent anti-Islam activist on Thursday said that she had been the plot's initial target, though Boston police cautioned that while Rahim had mentioned her name he seemed to have no concrete plans to attack her.

Pamela Geller, who identified herself on CNN as the possible target, organized a May event in Texas highlighting cartoons of the Prophet Mohammed, images that many Muslims consider blasphemous. Two gunmen attacked that event but were shot dead.

Boston Police Commissioner William Evans said it did not seem that Rahim had developed a specific plan to attack Geller.

"This was wishful thinking" on Rahim's part, Evans said on NBC's "Today" program.

Geller's group, the American Freedom Defense Initiative, is on the Southern Poverty Law Center's annual list of U.S. hate groups.

(Reporting by Scott Malone; Editing by Lisa Von Ahn and Steve Orlofsky)