Swimmer missing from race down New York's Hudson River In this July 23, 2013, photo provided by Jenny Warburg, Dr. Charles van der Horst, standing at center, joins a Moral Monday protest at the state legislative building in Raleigh, N.C. Police were searching Saturday for the retired medical school professor and AIDS researcher from North Carolina who went missing during a marathon swimming race down New York's Hudson River. Tim Tyson sits before Van der Horst. (Jenny Warburg via AP) NEW YORK -- Police were searching Saturday for a retired medical school professor and AIDS researcher from North Carolina who went missing during a marathon swimming race down New York's Hudson River. Authorities say Dr. Charles van der Horst, 67, was reported missing just after 3 p.m. Friday near the George Washington Bridge. Police say a man who was watching from the river bank saw van der Horst disappear and called 911. The New York City Police Department resumed searching for van der Horst on Saturday after suspending the search late Friday. Van der Horst was taking part in a multi-stage 120-mile (193-kilometre) race down the Hudson called the 8 Bridges Race. Organizers cancelled Saturday's seventh and final stage of the race. New York Open Water, the organization that runs the race, said in a statement, "Our thoughts are first and foremost with the Van Der Horst family and we ask that all respect their wish for privacy as they mourn this tragic loss."