The suspected gunman behind a bloody Bronx quadruple murder-suicide was a fun-loving local kid who played sports and worked construction before his life unexpectedly went off the rails. Kaseem Stukes, 44, went to elementary school at PS 36 and junior high at PS 125 in Unionport, and grew up with a tight-knit group of friends who were “just trying to make it,” childhood pal Felix Angomas said. But despite a gun rap earlier this year, friends and neighbors are shocked that he could be the monster