A lone shooter who opened fire on a U.S. Immigration and Customs Enforcement facility on Wednesday morning left agents with chilling messages explaining why their workplace was being targeted in the brazen attack. The gunman, who initial reports described as a white male, shot himself after being confronted by responding officers on a nearby rooftop. He used a sniper rifle in the attack, according to ICE Director Todd Lyons. At a press conference, FBI Special Agent in Charge R. Joseph Rothrock said the Dallas, Texas detention center was likely targeted because the shooter had a deeply-held animosity for ICE. “What...