Oct. 5: C123K cargo plane, part of the resupply operation set up by retired Air Force major general Richard V. Secord, is shot down over Nicaragua. Two American pilots killed; Eugene Hasenfus captured. Oct. 7: Businessman Roy Furmark warns CIA Director William J. Casey that funds from Iran arms sales have been diverted to the contras, Casey says. Early October: Lt. Col. Oliver L. North and Casey discuss the diversion of funds. According to North's testimony yesterday, he and Casey concluded things ought to be "cleaned up." North subsequently began shredding documents. Oct. 26-29: Shipment of arms to Iran. Hostage David P. Jacobsen is released three days later. Nov. 3: Ash-Shiraa, a Beirut weekly, publishes a story about former national security adviser Robert C. McFarlane's visit to Tehran. Nov. 7: North writes the first of several versions of a relatively accurate chronology of the U.S.-Iran arms sales. McFarlane's subsequent amendments to one version "radically differ from the truth," North says. Nov. 21: Attorney General Edwin Meese III informs national security adviser John M. Poindexter that the Justice Department will investigate the arms sales. North's secretary, Fawn Hall, helps her boss shred and alter pertinent documents. Nov. 22: Justice Department investigators find a memo about the diversion of funds in North's files. Nov. 25: Meese discloses the diversion of funds at a news conference. President Reagan announces the resignation of Poindexter and the firing of North.