An 18-year-old man was in critical condition after being shot Friday afternoon, the city’s 12th shooting since a 21-year-old was shot and killed Sept. 3.  Police responded at 12:27 p.m. to the area of Cavallo Road and Sunset Drive to multiple reports of shots fired.   Arriving officers found an 18-year-old man suffering from at least one gunshot wound. Officers immediately provided first aid to the victim until paramedics arrived. He was transported to an area hospital with life-threatening injuries. Police said the investigation is in its preliminary stages and evidence and witness statements are being collected. Since 21-year-old Elijah Scales was shot and killed on Sept. 3 in the 2100 block of Peppertree Way, six people have been wounded — three critically — in at least 12 shootings in Antioch. One of the victims was shot at a service for Scales on Monday in 1800 block of Cavallo Road — one of four shootings Monday.  Police said Tuesday they believe the shootings are related and asked for the community’s help in finding the suspects.    “This spate of violence will not be tolerated,” Interim Police Chief Brian Addington said in a statement Wednesday. “We have rearranged staffing and assigned two officers to patrol the Sycamore (Drive) Corridor for at least the next seven days. This effort aims to reduce gun violence and provide a sense of safety to the community and local businesses.” Police didn’t say Friday whether they believe the latest shooting was related to the others.  Police said anyone with information about the shootings can contact Sgt. Bill Whitaker at (925) 779-6876 or [email protected].