Premier League champions Arsenal were knocked out of the Carabao Cup after a stunning loss to fourth-tier Fleetwood Town following a penalty shootout Tuesday.

Bruno Guimarães had his spot kick saved by Jay Lynch before Fleetwood's teenage defender Conor Haughey lashed home an emphatic penalty to spark a pitch invasion at Highbury Stadium as the League Two side triumphed 5-3 in one of the greatest upsets in the competition's 66-year history.

- Drone halts play in Arsenal Carabao Cup game at 4th-tier Fleetwood

Asked what was going through his mind before taking the decisive penalty, Haughey told Sky Sports: "I don't know -- just pick my spot and put it in! Top corner and then just run.

"We've just beaten the Premier League champions, it just shows how good this team are."

It is the first time that reigning Premier League champions have been knocked out of the League Cup by a fourth-tier side. Eighty-four positions separate the teams in the English football pyramid.

The match finished 1-1 in regulation.

"I don't think it will [sink in]," Fleetwood manager Matt Lawlor told Sky Sports. "I've just told the players to enjoy it and we've got a league game on Saturday. I didn't want to be the bearer of reality, but we've got a game.

"I couldn't believe it. The biggest night in the club's history in terms of opposition coming to town and we've managed to beat the champions somehow."

Arsenal didn't field a full-strength team -- first-team stars such as Declan Rice, Gabriel and David Raya were missing -- but manager Mikel Arteta still picked a strong lineup containing seasoned internationals, with captain Martin Ødegaard even thrown on at halftime with Fleetwood leading 1-0.

Fleetwood, 18th in League Two, dared to dream after Fulham loanee Aaron Loupalo-Bi put them in front after 21 minutes against a much-changed Arsenal side struggling to find any fluidity.

Ødegaard's introduction changed the game as Arsenal looked much improved after the break, drawing level in the 50th minute when Viktor Gyökeres just about managed to turn in his first goal of the season.

But as Arsenal tuned up the heat without reward, their frustration boiled over as their teenage prodigy Max Dowman was sent off with five minutes left to play. Dowman appeared to get a rebuke from Arteta as he left the field.

There was still time for Lynch to make huge saves from Ben White and Ødegaard before it went to a shootout in which Fleetwood were perfect from the spot to secure their first ever win over a top-flight side.

Fleetwood now move into the quarterfinals of the competition for the first time. Following the win, Fleetwood players said they took inspiration from fourth-tier Grimsby Town's win over Manchester United in last season's competition.

"We looked at Grimsby beating Man United last year," goalkeeper Lynch said. "We compared it even though these are the champions. We thought 'if we lay it all out there, let's see what happens.'"

Fleetwood, which is a coastal town in northwest England, is most famous for being the team where former England and Leicester striker Jamie Vardy made his name. He was there for just one season and helped Fleetwood gain promotion out of the fifth tier, and into the English Football League, before getting a move to Leicester in 2012.

Arsenal have now been eliminated in their past two League Cup ties against sides from the fourth tier of English football, having been ousted by Bradford City in the 2012-13 quarterfinals on penalties. The north London side won their previous eight such matchups.

Arsenal also lost their previous penalty shootout -- against Paris Saint-Germain in the Champions League final in Budapest at the end of last season.

Information from The Associated Press, PA and ESPN Research contributed to this report.