Yes Rinky,
This "sell" very likely could have been whats called a "Stock Swap", where a person trades company stock they already own for option stock.
Say your company stock sells for $50 a share, and you have an ISO to buy 5,000 additional shares for $25 each.
Instead of paying $125,000 in cash to exercise the option, you could exchange 2,500 shares (with a total market value of $125,000) you already own for the 5,000 new shares. This strategy has the additional benefit of limiting your concentration in company stock.
dilen