Bezos buys. Strib reports. Strib at that link posts links to four key insider memos, to the outside.
Bezos before moving to Seattle to start his online retailing empire worked on Wall Street, including at the prestigious D. E. SHAW & CO. Presumably there are no insider trading fingerprints to the deal; Bezos knowing better from that background.
_____________UPDATE____________
Indications are Bezos and the Graham/Weymouth transaction plans were duly filed with the SEC. Presuming no regulatory impediment arises, and while Bezos is transacting a personal acquisition independent of amazon.com; readers may wonder whether Bezos owning the Big Paper in town will relate in any way to how taxing internet sales fares as an issue, in Congresses to come. Bezos states he has no particular agenda and intends to not involve himself in day-to-day publishing decisions. However, taxing of internet sales is not really a day-to-day issue in Congress either.