HOUSTON, Texas (KTRK) -- Police are urging people everywhere to use property transaction safe zones when meeting strangers to buy or sell items.Officers say meeting at police stations could prevent you from becoming a robbery victim, like this mother of four.The victim, who does not want to be identified, often used the OfferUp app to sell things like baby clothes, baby shoes and toys. On Monday, she used it for the last time."It's scary. It's scary. I could have lost my life," she told Eyewitness News.She posted a radar detector and agreed to sell it for $150. The buyer was in front of her house within a few hours."It was him and a young lady and a baby in the back seat," the victim said.She said the little boy was asleep. She and her husband were standing outside the buyer's white Cadillac making sure the radar detector worked and he talked her out of it."He said, 'Can I take a better look at it?' That's when I handed everything over and he sped off," the victim said.Her security camera got a good shot of him and the car. She called Houston police and learned she was one of several victims that day. There was one robbery before hers and three afterward including one that happened at a Shell gas station on the Eastex Freeway.That victim told Eyewitness News he met the same couple with a baby. They showed him a gun and took the iPhone he was selling. Then they sped off. He managed to get a short video of their car, the same white Cadillac.The female victim posted what happened and pictures of the male robber on OfferUp as a warning. She's worried someone will eventually get hurt."Hopefully he's caught and she's caught. I was lucky someone up there was watching me," she said.Anyone with information about the robbers or their vehicle is urged to contact Houston police or Crime Stoppers.