A man who reportedly tipped police to the identities of three suspected pharmacy robbers is now accused of participating in the Sept. 27 incident. Benjamin K. Rasmussen, 19, pleaded not guilty Wednesday to one charge of first-degree robbery. As part of a plea bargain, Ariel A. Arrieta, 21, told police in March that Rasmussen joined her, Jed L. Boles, 32, and William E. Higgins, 22, as they drove to the pharmacy, then shared in the pill proceeds. Initial reports said Rasmussen knew of the robbery but did not participate or receive stolen OxyContin. Higgins, Boles and Arrieta remain in jail on robbery charges. Rasmussen was booked Tuesday, then released on his own recognizance. Higgins also is charged with second-degree assault and witness intimidation for an alleged attack against Rasmussen in a Deer Park park on March 6. Higgins is accused of punching Rasmussen and calling him a “snitch.”