The plts of 2 cessna 182 acft took off from rwy 10 in formation. One of these, n6384a, had 4 skydivers aboard. After takeoff, the plt of n6384a discontinued formation flt & depd to the se, while the otr cessna depd ne. At about the same time, a piper pa-28, n4676r, was apchg the arpt with a dual student & instructor (cfi) aboard. Subsequently, the 2 acft converged & collided about 1-1/2 mi se of the arpt. No known witness saw the collision; the altitude & headings of the acft were not verified. During impact, the 2 acft became entangled & they impacted the ground at the same location. An investigation revealed evidence that the high wing cessna & the low wing pa-28 converged laterally, while on flt paths that angled toward each other.