The music was blaring on a February afternoon when Francisco Torres stopped by a Massachusetts barbershop, proclaiming he was half-angel, half-devil.

He wanted a dozen people to come outside the shop and shoot him with an automatic weapon stored in his car trunk. Before anyone could make sense of the request, Torres fled the shop and drove off. They never saw a weapon and he didn’t return.

“I didn’t get what he was saying but then I realized he was talking about a gun. I told him there are kids in here, why are you saying this,” said Saul Perez, who was visiting friends at the shop and noted that an employee called 911, ushered children into the back and shut down the shop. “I was spooked.”

The incident took place about a week before Torres would be arrested for attacking a flight attendant and attempting to open the plane’s emergency door on a cross-country United flight from Los Angeles to Boston earlier this month.

Confrontations on flights have skyrocketed since the pandemic started, with some altercations captured and replayed endlessly on social media.

In a video taken by a fellow passenger, Torres loudly threatens to kill people and promises a bloodbath before charging the front of the plane, where a group of passengers tackled him down to the ground to restrain him.

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Torres remains behind bars pending a mental health evaluation, with a judge ruling he “may presently be suffering from a mental disease or defect rendering him mentally incompetent.”

He objected to the evaluation through his federal public defender, Joshua Hanye, who didn’t return a call Thursday seeking additional comment. A relative for Torres would not comment on the case.

The flight attack was part of a decadeslong pattern of Torres demonstrating signs of a mental illness. He spent time in mental health facilities, according to lawsuits since closed that he filed in 2021 and 2022 against two hospitals in Massachusetts. Torres says he argued in one of the lawsuits that he was misdiagnosed for a mental illness and, in the other, that he was discriminated against for being vegan.

In December 2022, police confronted him at his house in Worcester County, where he was outside in his underwear saying he was protesting climate change, according to a police report. On another occasion in 2021, police responded to a call from his mother reporting that he was yelling “homicidal threats” out a window. He told police that he was in World War III and he had a special device giving him “super sonic hearing,” which he used to listen to his neighbors talking about him.

His case history demonstrates the challenges facing airlines and federal regulators when handling passengers like Torres. Especially since experts say data shows those with mental illnesses are more often the victims of crimes than those responsible for committing violent acts.

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Despite repeated run-ins with police, authorities said that he rarely acted violent. He once was accused of grabbing his mother’s arm, but those charges were dismissed. He didn’t legally own a weapon, even though he often talked about guns. And there were no signs of trouble when he boarded that cross-county flight last month, a passenger said, or during the first five hours in the air.

“He is really a nonviolent offender,” said Leominster Police Chief Aaron Kennedy, who is familiar with Torres from previous run-ins. “This guy was pretty mild.”

And even if past incidents raised red flags, experts said there isn’t a whole lot that airline companies can or should be doing. Airlines say they don’t share banned passenger lists with each other, though there have been a few cases so notorious that the passenger’s name became widely known.

The FBI maintains a no-fly list for people suspected of terrorism, to which special agents and other approved government employees can submit names for consideration.

People with mental illnesses are not prohibited from getting on a plane, according to Jeffrey Price, an aviation-security expert at Metropolitan State University of Denver. Federal law gives U.S. citizens “a public right of transit through the navigable airspace,” he said.

Legislation backed by airlines and their labor unions was introduced in Congress last year to create a new no-fly list including people who were charged or fined for interfering with airline crews. The bills died without hearings in the Senate or House, but backers plan to re-introduce them later this month.

Several Republican senators opposed the proposal, saying it could be used to punish critics of the federal rule requiring passengers to wear masks — even to “equate them to terrorists.” From January 2021 to April 2022, while the federal mask mandate was still in effect, the vast majority of unruly-passenger cases reported by airlines involved disputes over masks, according to Federal Aviation Administration figures.

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Some liberal groups also opposed the legislation, arguing that the current no-fly list of people suspected of terrorism is opaque and unfair.

The American Civil Liberties Union has sued the government several times over the last decade on behalf of people who didn’t know why they were on the list or how to be removed from it. The ACLU also has accused the FBI of putting some people on the list to pressure them to become informants in counter-terrorist investigations against Muslim communities in the U.S.

The captain of an airline flight can decide not to fly with a particular passenger on board, although flight attendants say this usually happens when a passenger appears to be drunk.

The government runs what it calls “trusted traveler” programs such as TSA PreCheck, which lets people who are fingerprinted and pass a background check speed through security without removing shoes, belts, jackets and laptops from their bags. People can be denied PreCheck for certain crimes, which extends to those who are found not guilty by reason of insanity. But of course people who are denied PreCheck can still fly.

Adding travelers like Torres to any no-fly list or barring them from a flight raises a host of logistical and constitutional questions. And determining who would get on a list would be controversial in a country that prides itself on protecting individual rights and keeping health information private by following strict HIPAA rules.

Plus, having a “mental health challenge” is “not a prediction, necessarily, that someone’s going to have outbursts, have unpredictable behavior,” said Lynn Bufka, a psychologist and the American Psychological Association’s associate chief of practice transformation. “That’s not going to be a good marker for determining whether or not someone should safely board.”

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Before Torres became agitated and threatened those around him, fellow passenger Jason Loomis said he didn’t exhibit any strange behavior during boarding and was quiet for the beginning of the flight. Hours later though, Loomis witnessed his outburst. Initially, he spoke with Torres to try to calm him down, but when Torres’ anger escalated, Loomis joined other passengers in restraining him.

Still, Loomis said he couldn’t envision keeping Torres off the flight in the first place. Instead, he said it was a reminder that society needs to take better care of mentally ill people.

“I know there has been a lot of talk about airplane security and safety these days, but this was a very rare occurrence,” Loomis said. “It wasn’t like he was shouting in the airport. He wasn’t threatening anything. He was perfectly fine and then something just snapped.”

The Associated Press contributed to this article.