Suspected Gilgo Beach serial killer Rex Heuermann was caught on video strolling down a Midtown sidewalk in the moments before plainclothes cops swooped in to arrest him, footage shows. Heuermann, 59, appeared oblivious as he walked along, with a messenger bag slung over his shoulder. Suddenly plainclothes officers can be seen stepping in front of, then surrounding the architect and taking him into custody, according to footage obtained by WABC.