Joe Levy is working hard to help avoid another mass school shooting tragedy. He says his technology, designed to spot a gun using existing CCTV cameras, could make a critical difference in future life-or-death situations. Seventeen people died in 2018 when a 19-year-old student opened fire at Stoneman Douglas High School, in Parkland, Florida, USA. Fifteen died in the Columbine High School massacre, near Denver, Colorado, in 1999 when a 17-year-old and an 18-year-old shot fellow students. And 22 people died in May of this year when an 18-year-old rampaged through the Robb Elementary School, in Uvalde, Texas – one of the worst school shootings in US history.