NBA great Dennis Johnson dead at 52

Dennis Johnson, a star guard for the Boston Celtics in the 1980s, is dead today at age 52, according to ESPN.com and the AP.

Johnson had been head coach of the Austin Toros, Boston's NBA D-League affiliate.

Earlier this week, Villanova star alumnus Allan Ray had been sent down to the Austin Toros. It had been hoped that Ray could learn from Johnson, the legendary guard.

Johnson's cause of death is not yet known, and his body will be autopsied, according to the Travis County (Texas) Medical Examiner's Office.

Update: ESPN's PTI just reported that Johnson died of a heart attack while coaching a Toros practice. This means it is likely that Allan Ray witnessed the event in person.