Smith, who will miss at least six to 10 weeks with two fractures in his jaw, accepted a $600 plane ticket from IK Enemkpali to appear at the reserve linebacker's football camp in Pflugerville, Texas, on July 11, according to sources. Problems arose when Smith did not show to the camp, which took place days after someone close to Smith was killed in a motorcycle accident in Miami, sources said.
After Smith did not attend, Enemkpali demanded that the Jets quarterback refund him the $600 he allegedly used to purchase the plane ticket. Smith told Enemkpali he would reimburse him the money, but he had not as of Tuesday morning. Enkempali confronted Smith on Tuesday about the money, and the confrontation ended in a punch and a broken jaw.
A source familiar with the situation told ESPN's Josina Anderson that at the start of camp, Smith approached Enemkpali, sensing tension between the two. The source said Smith confronted Enemkpali, tried to diffuse the situation and offered to pay Enemkpali the $600.
The source told Anderson "Geno initially intended to attend the event out of goodwill," adding, "Geno did not borrow $600 from [Enemkpali]. He volunteered to attend the event. Geno offered to pay the kid back from what was spent, to help him out."
Enemkpali, a sixth-round pick in 2014, was released immediately by the team, with coach Todd Bowles saying it's up to Smith if he wants to formally press charges. The coach also said he spoke to the team and then made the decision to let go of Enemkpali.
"It had nothing to do with football. It was something very childish," Bowles said in an opening statement. "He got cold-cocked, sucker-punched, whatever you want to call it, in the jaw. He has a broken jaw, fractured jaw.
"The team knows it's something we don't tolerate, something we can't stand. You don't walk up to a man and punch him in the face."
"You can call him every name in the book and point in his face and do whatever you want," Bowles said later, "but when you punch a man in the face, that's some serious stuff."
Enemkpali released a statement Tuesday afternoon saying he was sorry for his actions.
"I apologize to the Jets organization, coaches, teammates and fans," Enemkpali said. "Geno and I let our frustration get the best of us, but I should have just walked away from the situation. I deeply regret and apologize for my actions. It was never my intention to harm anyone. I appreciate the opportunity I had with the Jets."
"Once [Enemkpali] calmed down, he was very remorseful," Bowles said. "From Geno's standpoint, anytime someone punches you in the face unwarranted, you're going to be pissed off -- and he was pissed off."
Bowles, who was informed of the situation by a trainer, said Smith did not throw a counter-punch and that several players stepped in to break up the altercation.
Bowles said he was also upset with Smith regarding the incident with Enemkpali.
"It takes two to tango -- one to throw a punch, but two to tango," Bowles explained.
Cornerback Darrelle Revis agreed with that sentiment, saying, "I hold both of them responsible, just the way it played out."
Smith, who was the presumptive opening day starter, will have surgery, according to Bowles. There's no guarantee that Smith will regain the starting job when his recovery ends, Bowles said.
"My only goal is to heal quickly and get back to playing with my teammates so I can be the best QB possible for the NY Jets," Smith said in a statement.
He also took to Instagram, vowing to return.
A clearly annoyed Bowles said Enemkpali punched Smith over a trivial matter.
"It was something very childish, something sixth-graders could've talked about," Bowles said. "It had no reason to happen. If they want to tell you what happened, they can tell you what happened. I told them I wouldn't say anything about it."
"This isn't a UFC match," Jets guard Willie Colon said. "We're football players, not fighters."
This is not Enemkpali's first brush with off-the-field violence. At 19, while at a bar when he was at college at Louisiana Tech, a fight broke out and he punched an off-duty cop who was working security at the bar. On that night, Enemkpali had to be subdued first with pepper spray and then with a stun gun.
He was arrested and charged with battery on a police officer and disturbing the peace/drunk, according to court records. The charge was amended to simple battery, and he received a suspended jail sentence and was placed on 13 months' probation. He also was ordered to perform 32 hours of community service and to complete an anger-management course.
Bowles indicated that the Jets might add another quarterback. The current No. 2 is Bryce Petty, a rookie who has been struggling in camp.
Free-agent quarterback Tyler Thigpen will work out for the Jets on Friday, a source told Schefter. The New York Daily News reports that the Jets have also reached out to free-agent quarterback Rex Grossman, who last played in 2013 with the Washington Redskins.
Smith, entering his third season, was having an impressive camp. He didn't throw his first interceptions until Monday.
Free-agent quarterback Michael Vick, who spent last season with the Jets, reached out to Smith via Twitter.
Prayers up, wishin lil bro a speedy recovery @GenoSmith7 .."It's not whether you get knocked down, it's whether you get up." -Vince Lombardi— Mike Vick (@MikeVick) August 11, 2015
Before Smith's injury, the Jets were 3.5-point home favorites over the Cleveland Browns in Week 1. The Westgate SuperBook moved the number back to New York -3 (-120). The SuperBook kept the Jets' season win total at 7.5, but dropped the price on the over from -130 to -120.
The Jets began the week as 100-1 long shots to win the Super Bowl.
Information from ESPN.com's David Purdum contributed to this report.