David Wright and Nicholas Rovinski are accused of conspiracy to provide material support to ISIS, the Department of Justice said Friday.
Rovinski and Wright are accused of plotting with Rahim to carry out violent attacks inside the United States in support of ISIS, the extremist Islamic group that occupies parts of Iraq, Syria and Libya and which has encouraged its followers to stage "lone wolf" terror attacks around the world.
Rovinski, of Everett, Massachusetts, was arrested Thursday night without incident, according to Boston FBI spokeswoman Kristen Setera. He was scheduled to appear before a U.S. magistrate Friday afternoon. Wright, who is also charged with obstruction of justice, was arrested shortly after Rahim's June 2 death. He is set for a June 19 court date.
The plot unraveled last week when authorities -- who had been secretly listening in on Rahim's telephone conversations -- concluded an attack on police officers was imminent.
When officers confronted Rahim
, he pulled a knife, and after they initially backed away from him, officers fired upon the attacker, killing him.
Law enforcement believed Rahim, Wright and Rovinski had been radicalized by ISIS and initially planned for Rahim to behead conservative blogger Pamela Geller. But Rahim switched targets and decided to knife police officers instead, because they were more accessible, according to the FBI and prosecutors.
During questioning, Wright waived his Miranda rights and spoken openly with police, the FBI has said. In his arrest affidavit, Rovinski is not named but described as attending a meeting on May 31 with Rahim and Wright on a beach in Rhode Island, where the three discussed "their plans," including the idea of beheading Geller.
CNN contact with Rovinski
In March, Rovinski had shared with CNN his Islamist extremist beliefs and motivation to act on them.
A producer exchanged messages with Rovinski, and during the conversation, the Rhode Island resident described exchanges with an alleged ISIS fighter who urged him to come to Iraq and Syria and join the terrorist group.
The communications were part of research into Americans identifying with jihadists online. Rovinski told CNN he considered following the fighter's call.
On his Twitter account, the Rhode Island resident spoke out against the United States: "Living amung (sic) the enemy."
"Who wishes to see flag of tawheed upon white house," he wrote on March 28. Tawheed, a fundamental principle and saying of Islam, is also a favorite inscription on jihadi flags -- namely ISIS and al Qaeda.
In an online conversation, he said, "I am not violent at heart but push the wrong button and its (sic) not pretty."
On his Twitter account were messages directed at people connected with ISIS, including Mujahid Miski, the online alias of Mohamed Abdullahi Hasan, a former Minnesotan believed to be fighting with Al-Shabaab in Somalia.
Miski also had been in direct contact with Alan Simpson, one of the two shooters in the Texas attack on Geller's "Draw Your Own Mohammed" event in May.
Rovinski told CNN in the online exchanges that he would attend services at a mosque near his home but said he never shared his fundamentalist interpretation of Islam with his imam. Prior to his conversion to Islam, he said he was agnostic, but sought "truth and guidance" and found Islam.