Story highlights Group had four members, including Archer, tipster allegedly tells police

Someone told police that suspect Edward Archer had ties to group with "radical beliefs"

Police statement doesn't identify the group

(CNN) Philadelphia police say they're looking into a report that the man accused of trying to assassinate a police officer last week had ties to a group with radical beliefs.

Police issued a statement Sunday saying a citizen had stopped a Philadelphia police officer on the street and claimed the suspect, Edward Archer, had "an affiliation to a group with radical beliefs."

The statement doesn't name the group or say where it is located or whether the alleged association is past or present.

The tipster told police the group was made up of four people, including Archer, who was the least radical of its members, said John McNesby, the president of the Philadelphia Fraternal Order of Police, who viewed the police report on the information the tipster provided. That person also warned that the threat isn't over, according to McNesby.

The department and the FBI are looking into the claim "in an effort to verify the credibility of the information given," police said.

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