The Mountain Hawks (7-7, 2-1) took the lead 45 seconds into the game, and were ahead until Walker made the 22-foot 3-pointer to lift the Greyhounds (8-6, 2-1) to the win.
Walker finished with 23 points and four steals, while Jarred Jones (John Carroll) had 24 points, six rebounds and three steals for Loyola.
Lehigh, which was picked to win the Patriot League in the preseason poll, shot 57.1 percent from the field and led 60-42 with 13:52 left in regulation after a Brandon Alston 3.
UMBC 85, Binghamton 71: Jairus Lyles and Will Darley (Dulaney) each scored 17 points to lead the host Retrievers (10-4, 1-0 America East) past the Bearcats (9-7, 0-1).
The win extended UMBC's best-ever Division I start.
Lyles, who came in as the conference scoring leader at 22 points per game, was 6-for-13 shooting with Darley shooting 6-for-10. Joe Sherburne, who came in leading the nation in 3-point percentage at 55.7, made two of five from beyond the arc and had 14 points. Nolan Gerrity added 13.
UMBC led early but didn't put the game away until a 14-0 run left it ahead 76-55 with five minutes remaining.
Garvin blocked Junior Robinson's potential go-ahead layup with 10 seconds left and was fouled in transition with the game tied at 71.
Miles Wilson and Chris Wray each scored 18 for Mount St. Mary's.
College of Charleston 62, Towson 57: Cameron Johnson and Jarrell Brantley made four straight free throws in the final seconds to secure victory as the host Cougars (12-4, 3-0 Colonial Athletic Association) thwarted a late Tigers (8-8, 0-3) rally.
Towson led 30-27 at the break, but Charleston charged back to take the lead for good on a Brantley jumper at the 11:05 mark. That started a 12-6 run for the Cougars, who were up 58-53 with 56 seconds left.
Arnaud William Adala Moto had 15 points for Towson.
Loyola Maryland 62, Lehigh 58: Freshman Stephanie Karcz had a career-high 10 points and added 14 rebounds for the host Greyhounds (6-8, 2-1 Patriot), who held off a late rally by the Mountain Hawks (4-9, 0-3) to win.
1/2 minutes of play.