A pair of duck hunters caused a minor scare at the Pilgrim Nuclear Power Station early Saturday when security personnel heard gunfire coming from Cape Cod Bay, officials said Monday. According to the Nuclear Regulatory Commission and Plymouth police, the two hunters were licensed to carry firearms and to hunt and were not inside the marked-off security zone surrounding the plant on the bay side of the facility. But the operators at the plant did not initially know they were hunters. After hearing gunshots, plant security officials reported an “unusual event’’ to the NRC, the US Coast Guard, and Plymouth police.Todd Feathers can be reached at firstname.lastname@example.org. Follow him on Twitter at @ToddFeathers.