of passengers have been injured in a crash between two trains on the line between salisbury and grateleyltshire. dorset and wiltshire fire and rescue have declared a critical incident and the line will remain closed. everything went black and there were red flashes and everything, people started to panic, but nobody was seriously injured. we will continue to monitor that breaking news for you. now on bbc news, our world investigates the controversial technology that could help tackle america's growing gun crime problem. operator: 911, - state your emergency. man: itjust sounded like there were fires of gunshots. - how many shots? 15 or 16. on average in america, 50 people are killed every day with guns. do you feel safe here? no. in california, we have the worst gun violence. it's just terrible, man! one company, shotspotter, says its gunfire locator technology can help tackle this huge problem. shotspotter is the reason why we were able to apprehend him and stop that killing spree. but some have questioned how often the company gets it right. so, is that like a typical type of call out