SWAMPSCOTT – Police have issued a photo of a man they say posed as a buyer responding to a Craigslist ad and robbed an auto repair shop owner Friday of a watch reportedly valued at $12,000.Detective Sgt. Tim Cassidy said the suspect was described as a white male 6 feet 2 inches tall in his 20s or early 30s, weighing 195 to 205 pounds with short strawberry blonde hair. He was wearing a black shirt and dark-colored pants and sneakers, police said.The owner of Four Seasons Motor Group, 460 Humphrey St., said the suspect met him at the shop to buy his Rolex watch, which had been placed for sale online for $12,000. Cassidy said the two communicated first through the Craigslist ad and then by cell phone.Around 12:30 p.m. on Friday, the robber walked into the shop and pointed a black semi-automatic handgun at the owner and demanded the watch, police reported. The robber took the watch and said, “Don?t follow me,” and left on foot in the direction of Cedar Hill Terrace, where police believe a car used by the robber was parked. It was unknown if there was an accomplice.Police are investigating a possible lead on a brown Mini Cooper spotted nearby but were unsure whether the vehicle was connected to the incident.Charles Patsios, the owner of the building, who was present at the time, said he was unaware while the robbery was taking place. Patsios said the robber walked right by him as he left the auto shop.?The guy said, ?Have a good day? to me, right after he robbed a guy at gunpoint,” said Patsios.Cassidy said there were three other men in the shop, but the robber “wasn?t nervous at all.”Cassidy said this robbery is unrelated to the other two in Swampscott this week, the first on Saturday at Olympia Sports and the second at The Gap on Wednesday, in which robbers took “an undisclosed amount of cash.”?You have to be careful when you sell things on Craigslist,” said Cassidy. “You never know who you are dealing with.”Three robberies in the same week have some business owners feeling helpless.Paolina Lepore, whose restaurant, Caffe Paolina, isn?t far from the auto shop at 646 Humphrey St., said there?s not much she and fellow Swampscott business owners can do to protect themselves.?What can you do? Try to save your life if you can,” said Lepore. “You wish it never happens. Nobody can prepare for these things. How would you? It?s hard to predict.”Cindy?s Pizza and Subs Manager Valerie Foresta said it isn?t as much her store that she?s worried about.?If they?re going to do it, they?re going to do it,” she said, “but we have a lot of kids who come in here.”Anyone who recognizes the suspect is asked to call Swampscott police at 781-595-1111.