The Kansas City Chiefs lost a heartbreaker on Monday, falling to the Jacksonville Jaguars, 31-28, in a back-and-forth battle that came down to the final seconds.

Trailing by three points with just over eight minutes remaining in the game, quarterback Patrick Mahomes engineered a 12-play, 86-yard scoring drive that culminated in a 2-yard touchdown plunge by tailback Kareem Hunt.

The series, which ate up over six minutes of clock, put Kansas City in front by four points with only one minute and 45 seconds remaining in regulation, setting up Jacksonville's final – and game-winning – drive.

The Jaguars connected on multiple third downs on the series, including a 33-yard strike from quarterback Trevor Lawrence to wide receiver Brian Thomas that moved the ball to Kansas City's 24-yard line. The Chiefs still nearly thwarted the series when safety Bryan Cook picked off Lawrence in the end zone a few snaps later, but a pass-interference penalty wiped out the takeaway and instead set up Lawrence's go-ahead scoring scramble on the ensuing snap.

It was one of 13 penalties on Kansas City, which built a 14-point lead early in the game but allowed Jacksonville to rattle off 21-uanswered points between the second and third quarters. The Jaguars' final touchdown in that sequence, in particular, represented a 14-point swing as linebacker Devin Lloyd picked off Mahomes in the red zone and returned it all the way for a 99-yard touchdown.

The takeaway pushed Jacksonville ahead for the first time all night late in the third quarter, but to the Chiefs' credit, they continued to fight back. Cornerback Trent McDuffie intercepted Lawrence on the Jaguars' next possession, setting up a 5-yard, go-ahead touchdown by Hunt just two snaps later.

Jacksonville then answered with a field goal, but Kansas City looked poised to seize the victory when Mahomes led the aforementioned 12-play, 86-yard scoring series that pushed the Chiefs in front with under two minutes to play.

The Jaguars made a handful of clutch plays on their final drive, however, and – paired with some untimely Kansas City penalties – the series ended with Lawrence scrambling into the end zone for the go-ahead score.

Lawrence's efforts dealt Kansas City a loss on a night in which the Chiefs racked up 476 yards of offense, but ultimately came up short on the scoreboard.

"In this league, it's so close that those [mistakes] change games," Mahomes said. "So, we have to be better. We've lost too many games already. We have to find a way to be better as a team, come together and play better throughout the rest of the season."

The Chiefs will now aim to get back on track this upcoming Sunday in a matchup against the Detroit Lions.