Welch made one of two free throws with 50 seconds remaining to give the Bonnies a 69-59 lead before Richmond went on an 8-1 run capped by a 3-pointer from Blake Francis with 16 seconds left.
Welch made two free throws then Richmond's Tyler Burton made a layup and the score was 73-71 at seven seconds to go. The Spiders then fouled English and he made both free throws for a key four-point lead with four seconds left.
The win pulled the Bonnies into a third-place tie with Richmond with four games remaining in the conference season.
Saint Bonaventure faces Duquesne at home on Wednesday. Richmond plays at George Washington on Wednesday.
For more AP college basketball coverage: https://apnews.com/Collegebasketball and http://twitter.com/AP-Top25
Elements of this story were generated by Automated Insights, http://www.automatedinsights.com/ap, using data from STATS LLC, https://www.stats.com