With nine first-half points, the 6-foot-5, 180-pound senior swingman helped his squad build a 23-11 advantage. At the start of the fourth quarter, after briefly falling behind, Pope John Paul regained control with a 10-2 spurt.
"I really think it came down to senior leadership," Panthers coach Jack Flanagan said. "Coaches coach, and players win games. That's what happened."
At 8 p.m. Saturday at Villanova, PJP II (15-9) will vie for its first district title against fourth-seeded Upper Moreland, which ousted eighth-seeded Octorara.
Mahoney, who is hearing from a number of Division III programs, shot 5 for 11 from the field (1 for 2 on three-pointers) and 2 for 3 from the line.
"A big thing we wanted to do was get a lot of defensive rebounds," Mahoney said. "We wanted to keep them from getting second-chance opportunities."
The Panthers, who clinched their third straight berth in the state tournament, were ahead, 12-5, after the first eight minutes. In the second quarter, Mahoney's three-point play made it 21-7.
Down by 25-21 at the break, Glen Mills (14-10) responded with a 14-4 surge.
"Basketball is a game of runs," Flanagan said. "They make a run, and it's your job to make a run right back at them."
For the Panthers, 6-4 senior center Jamel Stinson (12 points, six boards) and sophomore guard Mike Cianciulli (12 points, three assists) also made key contributions. Senior guard Alex Plate chipped in five points, four rebounds, and three assists.
The Bulls shot a miserable 5 for 26 from beyond the arc. Senior guard Jah-bree Alleyne led Glen Mills, which was hurt by 16 turnovers, with 13 points, three assists, and two steals.
Pope John Paul II 12 13 7 16 – 48
Glen Mills 5 16 14 7 – 42
PJP: James Bleming 6, Mike Cianciulli 12, Jamel Stinson 12, Brent Mahoney 13, Alex Plate 5.
GM: Jah-bree Alleyne 13, Marcus Smith 6, Quadir Jones 6, Khafese Jones 5, Shiheem Spencer 8, Dawine Harmon 4.
Contact Rick O'Brien at firstname.lastname@example.org, or @ozoneinq on Twitter. Read his blog, "The O'Zone," at www.philly.com/ozone