To the Web’s volunteer detectives, they were the “Backpack Brothers”: two slender men in track suits spotted in photos of the Boston Marathon crowd.

“Seen together with bags, one near possible bomb site,” one user wrote of the men in an online spreadsheet that the online sleuths used to keep track of clues. In the “race/ethnicity” column, the two were described as “ethnic.”

“Bag pointing downward. Probably heavy,” another user wrote at That was accompanied by photos of the two and a diagram showing how one man’s backpack had a bulge that might have been a pressure cooker packed with explosives.

But the Internet had the wrong guys.

On Thursday, the Backpack Brothers turned out to be a pair of friends from the Boston suburbs. They had no apparent connection to the bombings. Neither did “Blue Robe Guy.” Or “Torn Pants.” Or “Mr. Cardigan” — other figures that amateur sleuths had also scrutinized in the crowd.

Instead, the Backpack Brothers showed the dark side of an audacious effort to crowdsource a murder investigation. By day’s end, the two men had been barraged on Facebook. Sought by the media. Featured on the front page of the New York Post.

And then cleared.

“It’s not me. I am not the person,” said Salah Barhoum, a Moroccan-born high school sophomore in Revere, Mass. He was the “brother” in the blue jacket. After learning he was under suspicion late Wednesday, Barhoum said he went to the police.

He said they didn’t know who he was. “It’s only people doing it,” Barhoum said of the parallel investigation online. “Only people.”

On Thursday evening, investigators released the first photos of their official suspects, two men seen wearing black backpacks near the bombing scene. Authorities were trying to harness the power of crowdsourcing for themselves, to turn the Internet detectives from their own clues to the official ones.

“The only official photos, which should be officially relied upon, are those you see today,” said Richard DesLauriers, the FBI official leading the investigation.

At, the flagship site for the unofficial investigation, users sought to comply. “At this point in time the only photographs that are allowed to be posted in this [page] are images that may contain the FBI’s two suspects — all others will be deleted,” one posted.

The Internet’s investigation had begun shortly after midnight Wednesday, as the photos of the marathon crowd began to appear online. In theory, this was the kind of thing that the online “crowd” was good at. A few months ago, for instance, Reddit’s “redditors” had identified a car used in a hit-and-run accident, using only a photo of one broken headlight.

This time, they set up a “single place for people to compile, analyze, and discuss images, links, and thoughts about the Boston Bombing.” Anonymous users pored through photos from online repositories like Flickr, searching for bags and bystanders that looked out of place.

They were not, of course, the only ones who got things wrong.

Media outlets focused on a Saudi national who had been wounded at the scene. The man was cleared. On Wednesday, CNN’s John King had erroneously reported an arrest in the case, describing the person arrested as a “dark-skinned male.”

But since the Internet’s amateurs did their work in public, their mistakes were public, too.

For a while, the Backpack Brothers looked like one of their strongest leads. In some photos, these two appeared to be carrying their bags, but in others, they didn’t.

On Thursday, the online crowd’s suspicions were echoed by the New York Post. “Bag Men,” the headline read, over a photo of the two. “Feds seek these two pictured at Boston Marathon.”

The newspaper story said that a picture of the two men had been circulated among law enforcement officials. On Thursday, the newspaper’s Web site posted a story that said the men had been cleared. But the paper stood by its original story.

“The image was emailed to law enforcement agencies yesterday afternoon seeking information about these men, as our story reported,” said a statement from Editor-in-Chief Col Allan. “We did not identify them as suspects.”

In the Boston suburb of Revere on Wednesday, Barhoum, 17, had noticed a strange flood of messages to his Facebook page. Some seemed concerned. Others seemed angry. “I received a message from some guy from Oregon, saying, ‘How could you do that? Did you even think about the people that were injured?’ ” Barhoum said.

Barhoum said he went to the Massachusetts State Police to tell his story. He and a friend had left for the marathon on Monday morning, intending to run all or part of the route. But their directions were wrong. Instead of arriving at the starting line in far-off Hopkinton, they wound up at the finish line in Boston.

“We decided to watch,” Barhoum said. “We saw . . . probably like 20 guys, and just walked to the [train] station.” He said he was back home when the bombs went off.

On Thursday, before the FBI released those pictures of somebody else, Barhoum went to a track meet. He noticed a man watching him, talking on the phone. “He was like, ‘I just saw the guy who was on TV,’ ” Barhoum said. “That’s when I got scared. And I started just to run.”

By Thursday night, however, he was old news. The online spreadsheet listed the Backpack Brothers as cleared. The Internet’s detectives had moved on to examine the FBI’s pictures.

“I think this is the dark hat from Suspect #1, right?” Reddit user “cicampbe” wrote, including a link to a black hat with a Bridgestone golf logo. For the moment, it looked like a real clue.

Julie Tate and Alice Crites contributed to this report.