John Paul Molesky, 64, a retired U.S. Park policeman who had served with the force's mounted patrol, died Tuesday in Arlington County. County police said the cause of death was still under investigation. c

A police spokesman said Mr. Molesky was pronounced dead at Arlington Hospital, where he was taken after his car left the road in the 2600 block of Columbia Pike and struck a building. It was not known whether Mr. Molesky had been stricken by an illness and died before the accident or had succumbed as a result of the wreck.

Mr. Molesky, who lived in Fairfx, retired from the Park Police in 1968 after 20 years of service. At the time of his death, he was employed as a courier by the Permanent Mortgage Co. in Washington.

He was born in Archbald, Pa. He served in the Pacific with the Army in World War II and moved to the Washington area after the war.

Mr. Molesky was a member of the Knights of Columbus.

His wife, the former Bonnie Norris, died in 1972.

Survivors include two daughters, Susan M. Williams of Woodbridge, and Paula C. Tice of Sterling, Va.; three sisters, Sophie Wolekers of Scranton, Pa., and Gladys Gill and Alice Battone, both of Fairfax; two brothers, Joseph of Fairfax, and Michael of Fenwick Island, Del.; two half brothers, William and Walter Fasceski, both of Fairfax, and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to Heroes Inc., Washington, D.C.