ST. PETERSBURG — A former Gibbs High School student was arrested for posting a photo on Snapchat showing someone aiming a gun and the caption, “don’t come to school tomorrow,” the Pinellas County Sheriff’s Office said.Hanlin M. Majewski, 18, of 6710 Cardinal Drive S, was taken into custody just after midnight Monday and faces one count of threatening communications or threats of mass shootings, the Sheriff’s Office said.Someone familiar with Majewski’s Snapchat account alerted authorities to the post at about 11 p.m. Sunday, an hour after it appeared. The image on Snapchat, the multi-media messaging platform, shows a male in a black tactical vest pointing what appears to be a black handgun at the camera with the caption at the bottom.Deputies contacted Majewski at her home and she acknowledged taking the photograph earlier Sunday and posting it with the caption, the Sheriff’s Office said. She said the subject was her boyfriend’s 17-year-old brother, holding a fake gun.Majewski told deputies she meant no harm by posting the image, the Sheriff’s Office said.The image was posted from a home in the 4300 block of 2nd Avenue N in St. Petersburg.Deputies made contact with the boy in the photo and recovered a black tactical vest and a black airsoft BB gun. The boy had been playing with the BB gun just before Majewski took his photograph, the Sheriff’s Office said.The parents informed deputies that the 17-year-old boy did not have access to any weapons or firearms.Deputies arrested Majewski and transported her to the Pinellas County Jail without incident.Majewski was a student at Gibbs High School until last school year, the Sheriff’s Office said. She now is a student at Florida Virtual School, the online school providing remote personal learning to public, private, and home-schooled students from kindergarten through 12th grade. The boy is home-schooled, the Sheriff’s Office said, and neither attends Pinellas public schools.