He moved with eerie calmness, following a workaday routine.  But the gunman who fatally shot a security guard manning an entrance of a SoHo federal building Friday was bracing himself for murder.  Prepared to carry out what investigators believed would have been a “mass casualty incident” that could have left scores dead, Kevin Downing boarded a bus in Fort Lee, N.J., before taking the subway downtown, according to a law enforcement source.  He was packing a small arsenal of weapons and chip on his shoulder, the source told the Daily News.  According to the source, who has reviewed security video, Downing calmly walked in the Houston St. entrance of the building.  He walked up to the metal detector and began emptying a plastic bag he had with him into a bin.  Idriss Camara, working overtime, greeted Downing before the deranged man casually pulled a gun and shot the Ivory Coast immigrant point point-blank in the head.  As Downing strolled past the entryway, he approached the building’s elevators as the doors to one opened, the video shows.  The witness instantly recognized Downing, according to a source. There was a “brief interaction” and the witness went back into the elevator in a hurry, the source said. Downing didn’t follow, and instead turned around and shot himself in the head, the source said.  Investigators will never know what he was planning, but they believe he was preparing for a “mass casualty incident” and changed his mind at the last minute.  “We don’t know just where he was going in the building, but he was probably looking to ignite a large casualty event,” a law enforcement source close to the case said. “In the end, this is a case of a very smart guy who thought he could do much better and was disappointed that he didn’t have a job or was at a better place in his life.”  U.S. Rep Bill Pascrell, whose office had tried to assist Downing in his fight with the federal government, said there was never any sign of mental illness from the killer.  “He was always polite, he was always thankful,” said Pascrell. “What made him snap? I don’t know.”  Relatives and friends of Camara were still reeling Saturday as they pondered a final resting place for the 53-year-old immigrant.  “It’s a big mess right now,” said family friend Abdou Diarrassouba. “It’s hard to imagine your daddy goes to work one day and then someone comes and tells you that he passed away.”  Camara, a married father of four, 20 years after chasing his American Dream to New York, may return to his Ivory Coast homeland for burial after his stunning death.  “We’re shocked,” said Imam Souleimane Konate, a cousin of Camara. “We came to America because for us, America is a safe place.  “Now we are asking ourselves, ‘Is this the American dream? Being killed in your job? For nothing?”  ON A MOBILE DEVICE? WATCH THE VIDEO HERE.
Relatives of the security guard murdered in a Manhattan federal building gathered Saturday to mourn his brutal slaying.