An employee of the NFL was reportedly "seriously injured" in the mass shooting that occurred at 345 Park Avenue in midtown Manhattan, home to the headquarters for the league. The office building, which sits on 52nd Street and Park Avenue, was the site of a tragic mass shooting that left five dead, including one police officer, when a gunman unleashed fire inside before taking his own life. NFL Commissioner Roger Goodell sent a message, obtained by Fox News Digital, to all league employees announcing the traumatic event.CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COM"As has been widely reported, a gunman committed an