TAMPA — Josiah Pinner had high school in his sights. With the winter break behind him, the 15-year-old Tampa boy was halfway through his final year at Buchanan Middle School. He was looking forward to taking his girlfriend to the school's eighth-grade dance and starting at Gaither High in the fall, said his mother, Joanne Rojas."He was my world," Rojas said through tears Saturday, "my only boy."Rojas confirmed to the Tampa Bay Times that Josiah was the boy fatally struck by an undercover Hillsborough Sheriff's Office deputy while trying to cross Florida Avenue on Friday. The Sheriff's Office has not released any names in the incident, which was still under investigation Saturday. An agency spokesman said no new information was available.ON FACEBOOK LIVE: Family and friends of Josiah Pinner gather for a vigil Saturday night in Tampa.The deputy was driving an unmarked sedan north on Florida Avenue about 6:30 p.m. and had the green light to cross the intersection with E 124th Avenue, according to the Sheriff's Office. The deputy saw a teen walking a bike across Florida and swerved to avoid him, officials said. But the sheriff’s vehicle ended up striking another teen. The teens were crossing the road north of the crosswalk, officials said.Rojas said she wants to know more about an account from at least one witness who told her the undercover deputy was speeding at the time of the collision and left immediately after the crash and came back shortly after. In a news conference after the crash, Chief Deputy Donna Lusczynski said the undercover deputy never left the area. Another deputy in a marked patrol car was also in the area and stopped at the scene.Investigators were working to analyze data on the car's computer to determine the undercover deputy's speed at the time of crash, Lusczynski said. Rojas said Josiah and his 14-year-old best friend had just left Josiah's father's house and were headed to the other boy's house to hang out. The friend lived in the Halliday Village mobile home park on the west side of Florida Avenue, Rojas said. They almost made it there when Josiah was struck."He's traumatized," Rojas said of the other boy. "He and my son were together every day."Rojas, who shared custody of Josiah with his father and lives about five minutes from the crash scene, said her son helped her around the house and looked out for his three little sisters, Diana, 12, Jaliyah, 10, and Iyanah, 7. He was their protector, Rojas said, and they looked up to him.In their last conversation, Josiah had called from school and told his mother that one of his sisters needed to stop playing around at school and focus.The boy loved to play basketball, cheer for the Bucs and the Rays and spent hours playing the video game Fortnite. He was excited that his father, Jay Pinner, had just celebrated the birth of a son."He said, 'Ha ha, I'm not the only boy anymore," Rojas recalled. "I said, 'It's okay, you're always going to be the oldest.'"The black pitbull Josiah got for Christmas and named Midnight seems to be grieving with the rest of the family, Rojas said.About 100 friends and family gathered at the crash scene Saturday evening for a candlelight vigil in Josiah's honor. Some wore red and black, his favorite colors, and T-shirts bearing photo images of the boy.As the crowd gathered around dozens of candles, two young teen boys sobbed together and Rojas let out anguished cries. Rev. Sheila Blanco-Pedrosa of Light of God Interfaith Church urged mourners to support the family and wait for results of the investigation.“Remember as group we are strong,” she said. “As a community we are strong. … Tampa strong. Josiah strong.”Stephanie Bailey, who lives in Halliday Village, said a number of kids in the area cross Florida Avenue on their bikes, going between neighborhoods and playing tag and manhunt.“We’re devastated,” she said. “I think there needs to be some more blinking lights up here to let these kids cross Florida Avenue safely. With the neighborhood populated with so many kids, how can you not have flashing lights?”Earlier Saturday, Rojas said she was working to balance her own grief with her responsibilities as a mother. "I have to hold it together for the girls," she said. Contact Tony Marrero at [email protected] or (813) 226-3374. Follow @tmarrerotimes.