Prosecutors have announced they will not seek criminal charges against a Boston officer and an FBI agent who fatally shot a man last year who they believed was plotting an attack against police.

Suffolk District Attorney Daniel Conley announced his findings in the case Wednesday.

Conley says the evidence proves "beyond a reasonable doubt" that 26-year-old Usaamah Rahim refused to drop a large, military-style knife when approached by investigators June 2, 2015 in the city's Roslindale neighborhood.

Conley says a recorded phone conversation from that morning revealed Rahim planned to attack officers in Boston. Rahim had been under surveillance for months as part of an investigation into his ties with ISIS.

Conley says his office reviewed dozens of witness statements and police reports and footage from surveillance cameras.