A religious 75-year-old grandfather mysteriously gunned down by a Queens lake last month may have been the victim of an antisemitic hate crime, the victim’s shattered family said Thursday as detectives continue to hunt for clues and a clear motive in the killing.Albert Itzkowitz was enjoying a warm Spring day by Kissena Lake in Kissena Park on the afternoon of May 18 — a bucolic spot where his family said he spent many afternoons — when someone shot him to death, police said. He had a beach chair, radio, sunglasses, and a crossword puzzle with him at the time. With...