SEATTLE — Fabio Heuring was standing outside a Seattle nightclub on a Saturday night and smoking cigarettes with a friend when a man bolting from a bouncer ran into them. The enraged man ripped off his shirt in the middle of the street and prepared to give Heuring's buddy a beating.

Just then, in swooped a bizarre sight: a self-proclaimed superhero in a black mask and matching muscle-suit. He doused the aggressor with pepper spray, much to Heuring's shocked relief.

A couple hours later, though, the superhero ended up in jail for investigation of assault after using those tactics on another group of clubgoers, sending pangs of anxiety through the small, eccentric and mostly anonymous community of masked crime-fighters across the U.S.

The comic book-inspired patrolling of city streets by "real life super-heroes" has been getting more popular in recent years, thanks largely to mainstream attention in movies like last year's "Kick-Ass" and the recent HBO documentary "Superheroes." And as the ranks of the masked, caped and sometimes bullet-proof-vested avengers swell, many fret that even well-intentioned vigilantes risk hurting themselves, the public and the movement if they're as aggressive as the crime-fighter in Seattle.

Some have gone so far as to propose a sanctioning body to ensure that high super-hero standards are maintained.

"The movement has grown majorly," said Edward Stinson, a writer from Boca Raton, Fla., who advises real-life superheroes on a website devoted to the cause. "What I tell these guys is, `You're no longer in the shadows. You're in a new era. ... Build trust. Set standards. Make the real-life superheroes work to earn that title and take some kind of oath.'"

It's not clear how many costumed vigilantes there are in the U.S. The website lists 660 members around the world. They range from members of the New York Initiative in New York City and the Shadow Corp in Saginaw, Mich., to a character named Nightbow who says he has patrolled the streets of Carlisle, England, for three years. http://www.reallifesuperheroes.org

Some take on their fictional identities while doing charity work.

Benjamin Fodor, better known as Phoenix Jones, is the most prominent face of the Rain City Superhero Movement, a collection of vigilantes who appeared in Seattle over the past year. Early on Oct. 9, about two hours after he saved Heuring and his buddy, the 23-year-old man charged a group of people leaving a downtown nightclub as a videographer trailed him.

From the shaky camera work, it appeared there may have been some kind of disturbance in the group. Fodor insists he was breaking up a fight when he hit the crowd with pepper spray; the people who got sprayed told police there had been no fight. He was briefly booked into jail for investigation of assault, but prosecutors haven't charged him yet. He appeared in court last week while wearing his superhero costume under a button-down shirt.

"Recently there have been increased reports of citizens being pepper sprayed by (Fodor) and his group," the police report noted. "Although (Fodor) has been advised to observe and report incidents to 911, he continues to try to resolve things on his own."

Fodor remained unapologetic after the court appearance, saying he's just like anyone else except that "I decided to make a difference and stop crime in my neighborhood." He invited members of the public to join him on patrol Saturday night.

Heuring, a 27-year-old shuttle driver from Auburn, is a fan.

"Without a question, there was a fight going to happen," he said. "It could have ended ugly had he not come in. He used good judgment in our case. He saw who was instigating it and who he needed to defend."

But many in the vigilante community point to Fodor's arrest as a watershed moment: As more people – often, young people – fashion themselves into superheroes, they risk finding themselves in similar situations where they wind up hurting innocent members of the public or being shot, stabbed or beaten themselves. Such negative attention could doom the movement, they say.

Stinson, who is 40 and says he has a military background, said that if the movement is to continue to grow, it needs to do a better job policing itself. He envisions a nonprofit organization that would have departments devoted to fundraising and building community trust and alliances. He also thinks there should be tactical superhero training – including how to take control of a volatile situation and defuse it.

Filmmaker Michael Barnett followed 50 real-life crime fighters for 15 months for his documentary "Superheroes." Many have great intentions, he said, but that doesn't mean their methods are proper.

"The police by in large appreciate an extra set of eyes, but they really, really want these guys to do it according to the law," Barnett said.

Masked crusaders began appearing in the 1970s with San Diego's Captain Sticky, who used his Superman-like costume to fight against rental car rip-offs and for tenant rights, Barnett said. They spread throughout the country in the 1980s and 1990s, and became more popular thanks to the faster communications and online support communities of the Internet.

Barnett said he met plumbers, teachers, cashiers and firefighters who leave their day jobs behind every night in the name of security. Their weapons include pepper spray, stun guns and batons. Relatively few have any combat training or any formal knowledge of how to use their arsenal, he said.

That concerns the professional crime-fighters.

"If people want to dress up and walk around, knock yourself out," said Seattle police spokesman Mark Jamieson. "Our concern is when you insert yourself into these situations without knowing the facts, it's just not a smart thing to do. If you think a situation warrants calling 911, call 911."

Not all of the vigilantes take a confrontational approach. A 53-year-old man in Mountain View, Calif., who calls himself "The Eye," keeps a low-enough profile that officers there have never booked anyone arrested with his help.

"The only reason I know him is because he's my neighbor," said police spokeswoman Liz Wylie. "He's a neighborhood watch block captain, a very good one at that."