Karl Otto Henson couldn’t wait to get his hands on the new iPhone when it was released in September 2016. Demand for the iPhone 7 Plus was so high at local stores that it sold out before he could get one. So the 23-year-old University of Missouri student came up with a simple plan: buy a different model to use temporarily, then sell it once the new iPhone was back in stock.

But nothing about the transaction he set in motion would turn out to be simple. For Henson, what started as an attempt to offload a gently used cell phone escalated into gunfire, and ended with his arrest as the first gun owner motivated to shoot at a perceived threat under Missouri’s new “stand your ground” gun law that went into effect on January 1.

Henson had his phone for sale on Facebook for about a month when 20-year-old Devonte Robinson messaged him about buying it. The two initially agreed to meet at Henson’s off-campus apartment on January 22. Henson then postponed the deal when he had trouble clearing his data from the device.

They rescheduled the meeting for January 23 and met in the front yard of a white two-story duplex in a cul-de-sac in north Columbia. Robinson looked at the phone and said that he needed to get his SIM card, and briefly disappeared behind the duplex. According to Henson, Robinson then returned to their meeting spot, examined the phone, and took off running, iPhone in hand.

Henson was carrying a handgun. (Police have not released information on the make and model.) He took it out, chased Robinson, and shot at him — seven times. Henson watched Robinson fall to the ground as he ran through a field before getting up and taking off again. At the time, Henson was unsure if Robinson had tripped, or been hit by one of his bullets.

Officers arrived at the duplex at 5:25 p.m., responding to a call about shots fired. They found Henson’s gun in the back of his car. There was no sign of Robinson. Later, the officers got word that a man with a gunshot wound to his left heel had checked into University Hospital.

“The only reason I thought it was OK to shoot at him while he was running away was because of what happened with the new year with the gun law change,” Henson told Officer Spirit Stevens, according to the probable-cause statement filed by law enforcement after the incident. “Something along the lines of ‘the old law, you weren’t allowed to shoot somebody when their back is turned to you,’” Henson says. He was detained and charged with armed criminal action and first-degree assault.

The shooting happened 23 days after Missouri implemented SB 656, as its “stand your ground” law is officially catalogued. The statute allows residents to use to lethal force if they feel their life or someone else’s life is threatened. The law does not, however, allow a person to use force to protect property. The old self-defense law required a shooter to retreat before firing. The new “stand your ground” statute removes that requirement and allows self-defense shootings in public places.

“Stand your ground” was met in Missouri, as elsewhere, with controversy and confusion. Supporters say it gives people more power to defend themselves. Opponents worry that it creates a dangerous “shoot first” mentality.

“This guy is the perfect example of somebody who just had no business carrying a gun without knowing the law,” says Tim Oliver, a concealed-carry instructor in Columbia. Oliver says he teaches the people who take his courses not only how to shoot a gun, but when to shoot it.

One evening in early March, roughly two dozen Missourians filed into a conference room at a Best Western in St. Charles. Early arrivals flipped through the handouts as others signed in near the door. All were there to learn how the state’s new gun laws affect them. Less than three months before Missouri adopted “stand your ground,” the state enacted a separate statute removing the requirement that gun owners secure training and a permit before carrying a concealed pistol.

“I’m putting on a seminar simply because I’ve gotten a lot of calls from clients since the laws have changed,” Wayne Schoeneberg, a criminal defense attorney, tells the crowd as the seminar begins.

Now that the state no longer requires firearms training in order to carry a concealed gun, education is up to the individual. That training reduces the risk of making a serious mistake, Schoeneberg tells the 20 or so men and women assembled, most of them white and middle-aged. What’s more, he says, “If force is ever used, the fact that you had the training will be to your benefit when law enforcement assesses your situation.”

Missouri was the first state to pass a “stand your ground” law since the shooting death of Trayvon Martin in Florida brought notoriety to such legislation in 2013. Before taking that step, Missouri law followed the “castle doctrine,” which says that a person may shoot an intruder to his home, if perceiving the situation as life-threatening.

Schoeneberg, for his part, is worried about gun owners understanding that the new, more permissive “stand your ground” law still has limits. “I think that people think this is a license to do more than they’re really allowed,” he says.

Schoeneberg once successfully defended a former sheriff’s deputy in a “castle doctrine” case. One morning, the deputy’s wife went out to the couple’s garage only to find a drunk man in her car. She ran back inside to tell her husband, who grabbed his handgun and called 911, telling the operator “You better get somebody out here before I shoot this bastard.” He shot the bastard.

A blond woman in a purple shirt, sitting toward the back of the conference room, raises her hand. “I had a girlfriend who lived out here in one of the random, isolated subdivisions, and she came home and she found a dude taking a shower in her shower.” The woman wants to know if it would have been OK for her friend to run to get her gun, run back to the bathroom, and shoot the man — “’cause she feared for her life.”

Schoeneberg considered the query. “The question becomes, then, is it reasonable to shoot a naked man in your shower?” he said. Several people laughed.

At the end of the seminar, a few attendees raised their hands to ask questions and comment, including Julianne Leimkiller, an instructor at Stellar Concealed Carry, who thanked Schoeneberg for affirming that gun owners are “still responsible for knowing the law.”

“Unless you’re trained or unless you take the time to read the law yourself and understand it, how are you going to be able to quote it if you’re standing there with a smoking gun?” Leimkiller asked.

After spending about a month in the Boone County Jail, Henson was released on home detention. He’s staying at his parents’ home in House Springs, Missouri, while he awaits trial for charges of armed criminal action and first-degree assault.

Before the incident, Henson was a junior studying fisheries and wildlife and working at MC Sports, a chain sporting goods store. Now, he faces felony charges. He used to go to a recreational shooting range in Columbia every week. He’s had to pause that habit: As a condition of his bond, he can’t be near guns, and says he tries not to think about them.

Henson thinks he’s going to win his case — “I have the best lawyers in the Midwest,” he says — but he knows what’s at stake if he loses. A felony conviction would mean he loses his voting rights. He’d also no longer be legally allowed to own firearms. “This is going to take a lot of my basic American rights away for defending myself,” he says.

Henson says that prosecutors want Robinson to testify against him. (Repeated attempts to reach Robinson for comment were unsuccessful.) The latest hearing in the case was scheduled for May 11.

Apart from court visits, Henson says he has no intention of returning to Columbia. When asked how a reporter could reach him to conduct a follow-up interview, he offered his email. He’d just gotten a new phone, and he couldn’t remember the number.