Fans of 'Riverdale' were in for a treat this week, as the penultimate episode of the series' first season finally revealed exactly who was behind the trigger of the gun that killed Jason Blossom (Trevor Stines) and sent the small town into a panicked frenzy.

KJ Apa leads the series as Archie AndrewsKJ Apa leads the series as Archie Andrews

For weeks, Archie Andrews (KJ Apa) and friends Veronica (Camila Mendes), Jughead (Cole Sprouse), Betty (Lili Reinhart) and Kevin (Casey Cott) have been trying to work out exactly who's responsible for the death of their former schoolmate, sometimes even pointing the finger at some of their most loved ones. When they got their hands on a USB stick that contained the truth however, none of them could believe what they had seen.

As they watched on the screen, the South Side Serpents - headed up by Jughead's father - had captured and tied Jason Blossom to a chair. He was in a bad way, but still very much alive. When one of the Serpents left the room, it was Jason's father, Clifford Blossom (Barclay Hope) who entered, pulling out a pistol and shooting his son clean in the head. A twist that some viewers saw coming, but one that was still very much shocking.

Lili Reinhart takes on the role of Archie Comics favourite Betty CooperLili Reinhart takes on the role of Archie Comics favourite Betty Cooper

'Riverdale' showrunner Roberto Aguirre-Sacasa has now shed a little light on the decision-making that went into bringing this story full circle, explaining that there had been four of the older characters in the frame at some point or another.

Speaking to THR, he said: "What we did was I went in with three likely suspects and three reasons why. One was FP Jones (Skeet Ulrich), one was Hiram Lodge and one was Clifford Blossom. As we were working on the season, Hal Cooper (Lochlyn Munro) also became a possible suspect."

The showrunner went on to explain that around halfway into the season, the decision to make Clifford the killer was settled upon, because "it felt like the ultimate subversion to that, the darkest, most taboo thing we could do, is a parent killing a child. Once we landed on that being the point of no return, about halfway through the season, we started to build to Clifford."

So now that Clifford has been exposed as Jason's killer and his lifeless body was found on the Blossom property, will the Blossom family be able to move on and enjoy their lives? No chance.

Aguirre-Sacasa added of the upcoming season 1 finale: "Cheryl has a shocking story in the finale, probably even darker than Clifford killing Jason. She's at her worst place emotionally that she's ever been. And by the way, she's already been in a fraught, frayed place. It gets even worse now."

Exactly how that's all going to play out remains to be seen, but we can be sure to get some answers in the 'Riverdale' season 1 finale next week.

More: 'Riverdale' Season 1 Finale Synopsis Promises Drama And Confrontation

'Riverdale' concludes Thursday on The CW in the US and on Friday on Netflix in the UK.