[Warning: The following contains spoilers for the series finale of Criminal Minds. Read at your own risk!]

It started with an unsub and it ended with a party. After 15 years on the air, Criminal Minds finally said goodbye on Wednesday evening with a two-hour finale that saw some old faces return, a gun fight, two explosions, and a champagne-infused goodbye party for an OG member of the BAU.

The first hour of the finale saw the team once again chasing Everett Lynch, also known as The Chameleon (Michael Mosley). They managed to corner him at a compound in the middle of nowhere, but after a showdown with his mom and a giant explosion as a distraction, Lynch was able to escape through a hidden tunnel in the basement. Reid (Matthew Grey Gubler) was the first to figure out that Lynch hadn't actually died in the blast, but he fell into a coma after sustaining a head injury in the blast and wasn't able to tell anyone the revelation before he became unconscious.

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Luckily, the team was able to deduce the same information once the coroner's report came back from the explosion scene. Unluckily, Reid was stuck on the floor of his apartment, revisiting old ghosts as his brain bleed continued. The familiar faces included Hotch (Thomas Gibson), Gideon (Mandy Patinkin), and Derek Morgan (Shemar Moore), via well-placed flashback sequences. Reid actually got to spend some time with the definitive Criminal Minds unsub, The Reaper (C. Thomas Howell), and his late girlfriend Maeve (Beth Riesgraf). Both were able to help him find out what he needed to rejoin the world of the living in opposite ways, while also reminding viewers of the darkest and happiest days of Reid's life, respectively.

In the meantime, J.J. (AJ Cook) found Reid at his apartment and got him to the hospital where doctors could monitor his injuries. The rest of the team caught on to Lynch after he abducted Rossi's (Joe Mantegna) wife. They met him at the airplane hanger where the BAU jet was stored. He and Rossi ended up in one last gun fight on the jet before Rossi was shot and fell from the plane, but J.J. came in with the sniper skills and sent a flare towards the plane's gas tank and the entire jet blew up, killing Lynch in the cockpit.

The Criminal Minds Series Finale Trailer Brings Back a Lot of Familiar Faces

To wrap up the series, the entire team met back at Rossi's for a party. Garcia (Kirsten Vangsness) surprised everyone and announced that she would be the one leaving the team to work for a non-profit that would require looking at a lot less gore. While everyone was sad to see her leave, her exit opened the door for a potential romance as Alvez (Adam Rodriguez) asked her out on an official date.

TV Guide spoke with Criminal Minds showrunner Erica Messer about saying goodbye to the show, blowing up the jet, and why now felt like the time to finally pull the trigger on Garcia and Alvez.

The cast of <em>Criminal Minds</em>The cast of Criminal Minds

This finale had a lot of emotions in it, and not all of them were good. Can you talk about the decision to have The Reaper come back and have a terrifying element in this final episode?
Erica Messer:
It was really important for us to make sure that we were staying true to the show itself, which was, you can't really have the light-hearted goodness throughout the show. It's tough to have the good and the bad. I feel Like The Reaper was one of our series-defining villains. It wasn't so much when he was introduced. He was a bad guy when he was introduced, sure, but it's what he did by the time Episode 100 rolled around. By changing the course of Hotch's life and existence, it really cemented our series into being something a little bit unexpected.

Hundreds of episodes later — which sounds insane — this recognizable bad guy still haunts the minds of our heroes...I was talking to C. Thomas while he was shooting, and he said the thing that he gets stopped on the street for most of all is playing George Foyett...I didn't know that before we came up with the story idea. And I thought, "Gosh, this was this was definitely the right call to bring him back."

There were also some heart-wrenching flashbacks in the episode. How did you choose those when you have over 300 episodes of material to choose from?
Messer:
That was really hard...I kept picturing, Reid, getting off the elevator and walking into the bullpen as he has done hundreds of times., and then walking to his desk, and this time, he hears voices that haven't been there in [multiple seasons]...I remember that shot [in the Season 1 finale] specifically was like a oner. I though that would be such a nice acknowledgement. It wasn't the pilot, but it was still the first season. It's still the space that we inhabit today, but so much has changed since that moment. To kick it off with that was then promising the audience, "Now anything can happen."

When did you decide that you were going to blow up the jet?
Messer:
That was something that has been talked about [during] the 15 seasons pretty regularly... It's just never felt right, to be honest. Also, financially, that means you may need to have a new jet set and that was never really in the cards...At the end of this, like most of our true villains, they directly affect a member of the team. So what was The Chameleon gonna do that was at that level? We hoped he wouldn't kill Rossi's wife. We were like, 'Please don't let that happen. Don't let it be like another version of Haley.' We didn't want Rossi to die when he got on the jet. We just kept thinking like, 'But what is what is it? What could he do what could be bigger? What could be whatever?' Then it was, 'Now is the time that we actually kill a beloved character.' That character, and location was the jet. Once we said that, it all just sort of fell into place.

Kirsten Vangsness, <em>Criminal Minds</em>Kirsten Vangsness, Criminal Minds

Why did you choose Garcia to be the one to leave the BAU?
Messer:
Garcia leaving was something that was always in my head. Garcia has been sort of the center of this — the thing that hasn't changed, the thing that hasn't missed episodes, right? Garcia has been there through the ups and downs of all of it. I asked Kirsten, "What would you think if Garcia was the one to leave?" She thought about it for a second and then said, "Yeah, that's the right move. That's the right move." It was sort of with her blessing that we, because we wrote this finale together, it was with her blessing that we actually pursued that.

That opened the door for Alvez finally asking her on a date. What made you want to go down that road now?
Messer:
It was another little rule that we had, an unwritten role, that we that we didn't have team members ever in a relationship together. I mean, they all have their own relationships, but it was never together. And we really enjoyed how Garcia was determined not to like Alvez because that would somehow be a betrayal to Morgan. Even though they're two completely different characters, we just thought there was so much fun that they've had over the last few years playing that. That was another thing Kirsten and I talked about like, maybe he asks her out. Maybe it won't ever be anything, but maybe it'll be something we won't be sticking around to find out. We're just planting that little promise of team members of the BAU are actually going to go out for more than just a group dinner or drink. The audience can imagine what that would have looked like.

If Shemar Moore had managed to come back for the finale, could it have been Morgan asking her out on a date?
Messer:
No, because we wrote him off to have this lovely life with his wife and kids. So I think that would have unraveled all of that and made it way too messy

Will we ever find out what Garcia wrote in the note that she left behind at her desk?
Messer:
No.

Criminal Minds' final season is streaming on CBS All Access.