Sa’eed Nelson’s half-court shot for American hit the back of the rim at the buzzer.
Paulius Zalys scored 19 points to lead the Leopards (10-16, 7-8 Patriot League), who have won five straight for the first time since the 2012-13 season. Petrie finished with 14 points. Justin Jaworski added 13 points and Lukas Jarrett had 11 points.
Nelson had 22 to points and seven rebounds for the Eagles (13-13, 7-8). Stacy Beckton Jr. added 13 points and seven rebounds. Sam Iorio had 12 points.
The Leopards improve to 2-0 against the Eagles on the season. Lafayette defeated American 84-79 on Jan. 19. Lafayette takes on Bucknell on the road on Sunday. American plays Army on the road on Sunday.