KANSAS CITY, Mo. — A long, frustrating night for the Detroit Lions inside Arrowhead Stadium ended with safety Brian Branch delivering an open-handed strike to Kansas City Chiefs wide receiver JuJu Smith-Schuster, setting off a brief fight among players from both teams.

After Kansas City’s 30-17 victory Sunday night, Chiefs quarterback Patrick Mahomes tried to give a high-five to Branch as they met near midfield. Branch walked past Mahomes, and Chiefs wide receiver JuJu Smith-Schuster took umbrage with the move, walking up to Branch and having a few words with him.

Branch responded by striking Smith-Schuster in his facemask, sending him to the ground.

“It was a childish thing, but I’m tired of people doing stuff in between the play and refs don’t catch it,” Branch said. “They be trying to bully me out there. I should have never did it. It was childish.”

Smith-Schuster leaped to his feet and went after Branch, who played despite an ankle injury that had kept him out of practice most of the week. Chiefs running back Isiah Pacheco tried to get between them, but Branch succeeded in ripping Smith-Schuster’s helmet off as dozens of players from both teams converged on the scrum.

“He’s a great player and he’s huge for [their] team,” Smith-Schuster said of Branch. “After the game, I expected to shake his hand and say, ‘Good game.’ But he threw a punch.”

Branch said he was blocked in the back by Smith-Schuster toward the end of the game in front of the referees and they didn’t respond.

“I could’ve got hurt off of that play,” Branch said. “I still shouldn’t have done that.”

Asked what he thought prompted Branch’s actions, Smith-Schuster replied, “I mean, me just blocking him.”

“I’m just doing my job,” Smith-Schuster said. “I play between the whistles.”

Eventually, coaches and players separated the parties, and they finally left the field for the locker room. Branch could be facing another hefty fine — he was docked $23,186 for face-masking and unsportsmanlike conduct penalties against Green Bay last month — and perhaps even a suspension.

“I love Brian Branch,” Lions coach Dan Campbell said, “but what he did is inexcusable, and it’s not going to be accepted here. It’s not what we do. It’s not what we’re about. I apologized to Coach [Andy] Reid and the Chiefs, and Smith-Schuster. That’s not OK. That’s not what we do here. It’s not going to be OK. He knows it. Our team knows it. That’s not what we do.”

Smith-Schuster came away with a bloody nose.

“The guy came up and hit JuJu for what looked like no reason,” Reid said. “That’s tough, and he did pretty good damage on JuJu’s nose.”

Veteran Lions defensive lineman DJ Reader said he planned to talk to Branch once the emotions from Sunday die down.

“We’ll have that conversation. It’s hard to have that conversation right now because everybody’s trying to have the conversation,” Reader said. “I’m sure I’ll get a chance to talk to him, but it’s tough because he’s got that stinger for a reason as a player and you don’t ever want to take that away, but you also want him to be smart. Not only for us, but also for himself. To protect his money, to protect him.”

The loss snapped a four-game winning streak for Detroit, which was trying to pull off a rare feat by winning two consecutive games in Arrowhead Stadium. Instead, the Lions allowed 355 yards of total offense, forced just one punt and didn’t make the stops they needed late in the fourth quarter to give their offense a chance to mount a comeback.

Jared Goff finished with just 203 yards passing, though he had touchdown throws to Jameson Williams and Sam LaPorta. Amon-Ra St. Brown was held to 45 yards receiving. Jahmyr Gibbs needed 17 carries for 65 yards.

“That’s a physical team, and they have a mentality that they come in to play with, and we’re going to match that mentality,” Mahomes said. “We’re not afraid to go up against anybody. That’s the mentality Coach Reid brings every single day, and we’re going to match the intensity of whoever steps on that field.”

ESPN’s Eric Woodyard, Nate Taylor and The Associated Press contributed to this report.