Harrison shot seven of 11 from beyond the arc and poured in 29 points to lead all scorers and take down DePaul (11-10, 2-7).
"We did a bad job of getting back in transition and we didn't find him," DePaul sophomore Moses Morgan said of Harrison. "A few times he got open looks."
"We allowed (Harrison) to get going," said DePaul coach Oliver Purnell. "Once he got going, then he got aggressive."
St. John's (10-12, 4-6) had four players finish in double-figures. God's Gift Achiuwa added 15 points off the bench. Chicagoan Phil Greene scored 14 pts. and Amir Garrett contributed 12 points in the winning effort.
Turnovers proved costly for the Blue Demons in this one. St. John's managed to score 25 points off of 18 DePaul turnovers.
"With three or four minutes to play, I felt like we had some semblance of control, then inexplicably we didn't handle pressure very well," Purnell said.
Cleveland Melvin led the way for DePaul with a double-double of 22 points and 11 rebounds. Brandon Young recorded his first career double-double with 13 points and 11 assists.
One bright spot for DePaul was Moses Morgan's contributions off the bench. Morgan shot five of nine from beyond the arc to finish the night with 19 points.
"Coming into the game I knew I was going to get my shots, because they play that zone," said Morgan. "I worked in practice just practicing those shots from the top of the key and the left wing."
The Blue Demons were without the services of senior guard Jeremiah Kelly who was a late scratch from the starting lineup.
"I heard right before the game that he was struggling," Purnell. "I asked the trainer. She said it was muscular. She thought he could warm up and possibly go and he said he couldn't."
DePaul now goes out on the road to Cincinnati where they will face the Bearcats on Saturday night.
DePaul sophomore Moses Morgan got off to a slow start as a freshman at DePaul, but certainly came…