WARWICK, R.I. » A Rhode Island man was arrested Thursday in connection with the probe into a Massachusetts man who was fatally shot by terrorism investigators as they sought to question him about a possible plot to kill police officers.

Nicholas Rovinski is expected to appear in federal court Friday, when the charges against him will be announced, U.S. Attorney Carmen Ortiz’s spokeswoman Christina DiIorio-Sterling said.

Rovinski, of Warwick, was taken into custody Thursday night without incident, Boston FBI office spokeswoman Kristen Setera said. His house was searched by federal officials last week.

Rovinski couldn’t be reached for comment while in custody on Thursday night. A telephone call to his house rang unanswered, and a woman inside yelled through the front door to a reporter outside, "Get out of here."

Federal authorities say Boston resident Usaama Rahim plotted for at least a week to attack police. An FBI affidavit supporting a criminal complaint against Rahim’s nephew David Wright says Rahim, Wright and a third man met on a Rhode Island beach "to discuss their plans."

Rahim, who had been under surveillance, was confronted last week because he had bought knives and talked of an imminent attack on "boys in blue," the FBI said.

The FBI said Rahim, who had previously discussed beheadings, bought three fighting knives and a sharpener on or before May 26 and told Wright he would begin trying to randomly kill police officers.

An anti-terror task force of FBI agents and Boston police officers, faced with an imminent threat, confronted Rahim on a sidewalk and fatally shot him when he refused to drop his knife, authorities said.

Boston police Commissioner William Evans said officers confronted Rahim because "military and law enforcement lives were at threat." He said the officers "made the right call," drawing their guns only after backing away and giving Rahim "multiple chances" to drop the military-style knife he was holding.

Rahim’s relatives have disputed investigators’ version of events, citing a blurry surveillance video released by police. They said the video showing the terror investigators fatally shooting him doesn’t show him brandishing a weapon or approaching officers aggressively. They said he was not the initial aggressor and did not appear to be breaking any laws as he walked toward a bus stop on his way to work on June 2.

Wright, of Everett, Massachusetts, was arrested last week on a charge of conspiracy with intent to obstruct a federal investigation. He’s in custody pending a June 19 hearing.

Prosecutor Stephanie Siegmann said Wright posed a serious risk of fleeing or obstructing justice if not held pending the hearing. Wright’s attorney, Jessica Hedges, denied that, saying he has deep roots in the Boston area and an "incredibly loving and supportive family."

Hedges urged the government to be "as transparent as possible" and "abide by the law" as it investigates this case, saying "we have serious concerns about that already."

AP Legal Affairs Writer Denise Lavoie contributed to this report from Boston.