The resilient Pats never led until the end, erasing deficits of 1-0, 2-1 and 3-2.
It was former Hitmen defenceman Aaron Hyman who forced overtime for the visitors netting a power play goal with 8:54 remaining in regulation. Cole Dubinsky and Jake Leschyshyn rounded out the scoring for the visitors.
Riley Stotts, Jake Kryski and Kaden Elder provided the Hitmen goals while Mark Kastelic added a pair of assists.
Calgary outshot Regina 32-22 with both teams going 2-6 on the power play.
The Pats are back on home ice Wednesday to take on the Spokane Chiefs at 7 p.m. at the Brandt Centre. Tickets are available at reginapats.com, the Brandt Centre Box Office and at any Regina Safeway, where Fun Zone tickets are $13 plus tax. The game will be broadcast on Access TV and 620 CKRM.
(With files from HitmenHockey.com & ReginaPats.com)