Thornton, who scored 23, needed just 14 points to reach the record of 2,052 and broke it with the second of two free throws late in the first half. Set in 1950 by Chet Giermak, it was the longest-standing program record in Division I.
William & Mary (18-10, 12-5 Colonial Athletic Association) broke away with 15-2 run in the first half to carry a 28-15 advantage into the break. Towson cut the gap to five when Four McGlynn hit a 3-pointer with 3:28 left, but then went scoreless the rest of the way.
Tarpey tied a career-high with 13 rebounds, to get his ninth double-double of the season, and blocked five shots.
McGlynn led Towson (12-18, 5-12) with 13 points.