A Riverside County man has been arrested for allegedly robbing at least two mail carriers, officials said.

Nicholas Green was indicted earlier this month for his alleged involvement in two robberies of USPS letter carriers and procession of postal keys and stolen mail, according to the U.S. Postal Inspection Service.

Between March 16 and Nov. 16, five USPS carriers in Moreno Valley and Riverside were robbed under similar circumstances, officials said in a news release.

In some cases, the suspect brandished a gun and demanded the carrier’s postal keys. The suspect also allegedly used threatening notes demanding USPS keys from the letter carriers.

Postal inspectors searched Green’s home and found USPS postal keys, mail for people other than him, checks and other personally identifiable information that didn’t belong to him, officials said.

Authorities continue to investigate the other robberies and ask for the public’s help in identifying any additional possible suspects. Anyone with information is asked to contact the Postal Inspection Service at 877-876-2466.