ORLANDO, United States (AFP) — A top US lawmaker said Thursday authorities were probing the Facebook activity of the Orlando nightclub shooter, after an investigation found Omar Mateen made extremist posts during the massacre and searched for news of his attack. Ron Johnson, the Republican chairman of the Senate Committee on Homeland Security, sent a letter to Facebook chief Mark Zuckerberg Wednesday asking the company to share specifics of five accounts apparently used by Mateen. […]