Gangs on Thursday opened fire and hit a U.N. helicopter, forcing it to land in Port-au-Prince in the latest attack in Haiti’s capital as violence surges once again. No one was injured as several rounds of gunfire hit the helicopter that was carrying three crew members and 15 passengers, according to a U.N. source who was not authorized to confirm the incident. The helicopter, which had departed from Port-au-Prince before it was attacked, landed safely, the source said. The attack comes five months after Haiti’s main international airport reopened following coordinated gang attacks that forced it to close for nearly