One of latest citizen vigilantes is a 23-year-old Seattle man, Benjamin Fodor, who - wearing a black mask and matching full-body outfit and conveniently followed by a videographer - confronted a man who was menacing another person. “Phoenix Jones,” as Fodor called his superhero persona, doused the aggressor with pepper spray - but later also sprayed some rowdy partygoers and was arrested for assault.

Indeed, law-enforcement agencies take a dim view of vigilantes. Few of them have combat or weapons training, the police say. The avengers sometimes assault innocent people. And they’ve been known to go overboard with their righteous zeal, beating citizens for littering or damaging cars whose drivers are thought to be speeding through school zones.

“If you want to dress up and walk around, knock yourself out,” said Seattle police spokesman Mark Jamieson. “But inserting yourself into situations without knowing the facts is just not a smart thing to do.”