Omar Mateen, the gunman who left 50 dead when he stormed a gay nightclub in Orlando on Sunday, was an employee of the private security company G4S. What could or should the company have known to alert it to the risk that this individual would turn into a mass killer? John Murray Brown puts the question to the FT's Gill Plimmer and Jonathan Guthrie. For information regarding your data privacy, visit acast.com/privacy