Defreitas, 63, who immigrated to the U.S. more than 30 years ago from Guyana, was in custody Sunday pending a bail hearing, was arrested two days earlier in Brooklyn.
Ibrahim and another suspect, Abdul Kadir, were in custody in Trinidad awaiting extradition hearings. Officials identified Kadir as a former mayor of a Guyanese town and a member of the country's Parliament.
Authorities in Trinidad were still seeking a fourth suspect, Abdel Nur.
Authorities said the JFK case and last month's arrest of six men suspected of plotting to attack soldiers at Fort Dix, N.J., illustrated the need for inside information.
Is this what they mean by fighting them there so we don't have to fight them here? Looks like that plan is going about as well as the fighting them there part of this.
