PROVIDENCE, R.I. - In a tiny room on the fourth floor of Brown University's student center, Sunil Tripathi's family is waiting for him to come home.

The Brown student and Radnor native went missing a month ago, and the Tripathis have been plastering the town with photos ever since. Nicknamed "Sunny," the 22-year-old smiles from the windows of campus eateries and downtown businesses. In the student center, his family has been running Facebook and Twitter campaigns, looking for any clues into his disappearance.

Then, on Thursday night, there was a flurry of activity. Sunil's name was trending on Twitter. Users on Reddit and Facebook were posting his familiar smile.

But their motivation for doing so was worse than the Tripathis could have imagined. For a few horrifying hours, the Internet seemed to think their son was one of the Boston Marathon bombers.

FBI sources in Providence dismissed those allegations Friday afternoon, saying Tripathi was "not a suspect whatsoever." In a matter of hours, Sunil Tripathi went from being the most wanted man on Twitter to a curious footnote in a case that has drawn the attention of the world.

"I never believed it, from the beginning," said Ravi Tripathi, 26, Sunil's brother.

Judy Tripathi, 60, Sunil's mother, wiped away tears on a couch in the student center and described her son as a quiet, gentle young man who carried bugs outside the house rather than killing them. The family relocated to Providence from Radnor a day after his disappearance March 16 and hasn't left since, she said.

"He is the sweetest kid in the world," Judy Tripathi said. "To see his name smeared is such an abomination."

The Tripathis aren't quite sure how Sunil captured the Internet's attention - moderators on Reddit, who later apologized to the family, claimed that they heard his name on a police scanner. Hundreds of Twitter users retweeted that Sunil's name had been broadcast on a scanner. Ravi Tripathi hypothesized that online sleuths might have seized on the fact that Sunil's case had already received media attention because of his disappearance.

For the family, the Internet onslaught began after images of the two suspects in Monday's Boston Marathon bombings were released by the FBI. Dozens of posts began appearing on the Facebook page claiming he was the bomber.

"There's the beauty of social media - which we experienced in the first two weeks of the search," Ravi Tripathi said. "And, in this case, it was the negative side."

Family members began deleting the comments, post by post, until they realized that would take them hours. They called the public safety department at Brown, Providence police, and the FBI, and shut down the Facebook page. It has now been restored.

Meanwhile, the FBI had been receiving independent tips on Sunil, Ravi said. So had Radnor police, who also contacted the FBI. At 3:30 a.m., Radnor Officer Mark Stiansen showed up outside the Tripathis' house. He had heard reports of Sunil's possible involvement on Big Daddy Graham's sports-radio talk show and drove to the family home anticipating a large media presence.

News vans clustered outside the house in the predawn darkness, anticipating a major scoop. In Providence, the Tripathis were dumbfounded.

"At a lot of moments we put the two pictures together and just started laughing," Ravi Tripathi said. At one point, he said, he found a photo of himself online implicating him as the second bomber. "It almost became comical."

By the time the sun rose, Sunil's name had been cleared. Officials released the names of two suspects in the bombing: Dzhokhar A. Tsarnaev, 19, and his older brother, Tamerlan Tsarnaev, who was killed in a firefight with police in the wee hours of Friday morning. Dzhokhar Tsarnaev was arrested Friday night.

In Radnor, reporters trickled away from the Tripathis' household as the story in Massachusetts grew more extraordinary by the minute. Local officials tried to dispel the last of the rumors. At Radnor High School, principal Mark Schellinger held an assembly to address the rumors and announced that the FBI had informed him the reports about Tripathi were false.

"The assembly was to make students conscious of rumor and innuendo that's reported through online and social media, and we wanted to acknowledge that this rumor was spreading," said Michael Petitti, communications coordinator for the Radnor School District. "We're trying to be proactive."

"We feel for the Tripathi family," he said. "They really didn't deserve the compounding of their grief."

Brown released a statement as well, calling the online allegations untrue and adding that the school's "thoughts are with the Tripathi family, who have had to endure additional pain."

The Tripathis say they are grateful to their supporters in Providence and Radnor - Brown has provided meeting rooms to help them organize search efforts, and friends and family in Pennsylvania and across the country have helped spread the word.

Sunil suffered from depression, but his sister said his condition had not worsened in the weeks before he vanished. He left a note that hinted at suicidal intent, but family members have said the note was short and vague and gave no hint to what happened. When last seen, the 6-foot-tall Sunil was wearing blue jeans, a black ski jacket, glasses, and an Eagles beanie. He left his cellphone, wallet, and credit cards at his apartment.

Though they are shaken by Thursday night's ordeal, family members said, they are moving forward.

"The biggest thing is trying to turn this into positive, stimulating efforts," Judy Tripathi said.

At the very least, she said, there is a chance that amid the feeding frenzy on the Internet, the news trucks on his front lawn and the frantic scramble to confirm the Boston bomber's true identity, Sunil might have spotted his own face on a Reddit forum or a Twitter feed and decided to come home.

On Friday, they were posting photos on Facebook of messages to Sunil written on their hands - "I miss you"; "I love you"; "I can't wait to see you."

"Our biggest thing is to get his story out there," Judy Tripathi said. "The more eyes the better."

Contributing to this article were Inquirer staff writers Kathy Boccella, Mari A. Schaefer, Joseph A. Gambardello, and Susan Snyder.