In the early hours of 16 March Sunil Tripathi left the apartment he shared with other students on Angell Street in the Rhode Island city of Providence and walked into the darkness. At 1.33am a CCTV camera caught him pacing across a zebra crossing, hands pushed inside the pockets of his ski jacket, and then he was gone.

Aware the 22-year-old student had been suffering from depression, the young man’s family quickly raised an alarm, getting in touch with the police, student organisations and even the FBI. They organised searches, appealed for help on social media and uploaded a cheery, home-made video on to YouTube urging “Sunny” to come come home.

Last week, a lot of people thought they had seen Sunil Tripathi. Indeed, some people were so convinced he looked like one of two men identified by police as suspects in the Boston bombing that even before officials had named the two suspects, countless numbers of people were claiming the young man was the subject of a massive, unprecedented manhunt.

Download the new Independent Premium app Sharing the full story, not just the headlines

Then, just as quickly, when police revealed the men they were hunting were the Chechen-born brothers Tamerlan and Dzhokhar Tsarnaev, the matter of the young man of Indian background was hastily dropped. And yet Sunil Tripathi is still missing.

“The search is still on and we are trying our best to make it strong,” Mr Tripathi’s sister, Sangeeta, told The Independent this week. “After the events of last Thursday and Friday, we are launching our message back to the community and trying to channel the general public... The short of it is, we are still at it.”

The story surrounding the false identification of Sunil Tripathi is a cautionary reminder of how the pervasive reach of social media can be used for both good and bad. It is an insight, too, of how prejudice might cloud judgement and reason.

Sunil Tripathi is six feet tall, weighs 130lbs and has brown hair and brown eyes. When he went missing last month he was wearing blue jeans, glasses, a black Eastern Mountain brand jacket and a woollen hat bearing the insignia of the Philadelphia Eagles American football team. Twenty minutes before leaving his apartment, located next to Brown University in Providence, he had been using his computer and when he walked out of the door he left behind his mobile phone, identification card and wallet.

Although he was born and raised in Radnor, Pennsylvania, the young man had been living in Providence since 2008 and he followed both his sister and brother, Ravi, in enrolling at the Ivy League college to study philosophy. He loves chess and music and his family say he is a talented saxophonist

“Sunil is a capable and well-liked student,” said Margaret Klawunn, vice-president of student services at Brown, which has been helping in the search for Mr Tripathi and distributing flyers. “There is a lot of support from the Brown University family.”

Early last year, Mr Tripathi received permission to suspend his studies after suffering from bouts of depression and his family said they were in regular contact with him. When police searched his student digs, they found a note – “brief and vague” – that added to the family’s worries. And yet his family say people who spoke to him the day before he went missing said there was nothing unusual about the way he was behaving.

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

As part of the effort to reach out to him directly, his family members created a bouncy, two-minute video in which his friends and relatives recalled happy experiences they had shared with him and voiced their hope such experiences could soon be repeated.

In the video, his sister displays a Zanzibar FC soccer shirt she had bought him for him, an aunt recalls a meal in which they shared spinach calzone, a friend remembers a trip they took to Florida’s Hammock Beach while his mother, Judy, says: “One of the things that I remember, that I would like to do with you again, is to lie with you on your pillow mountain.”

Towards the end of the video message, Mr Tripathi’s father, Akhil, originally from the Indian state of Uttar Pradesh and who runs a software company, says simply: “Come back son. Call us. Love you – Dad.”

Mr Tripathi’s sister said the family had decided upon the video as it offered the chance of connecting with Mr Tripathi at a visceral level. “We wanted to speak directly to Sunny and to let people know a little about his story,” she said.

Precisely how Sunil Tripathi went from being the subject of a missing person’s search by a loving family to someone supposedly wanted by thousands of police and SWAT team officers remains unclear.

But it appears that speculation started on the social news site Reddit. Several of those in the US who claimed on the forum last Thursday evening local time that he was the man wanted by police, said his name had come up in conversations between officers on the police scanner.

One woman claimed she had gone to Radnor high school with Mr Tripathi and that images provided by police “looked like him” while Kevin Michael, a cameraman with a Hartford affiliate of the CBS television network said on Twitter: “BPD scanner has identified the names: Suspect 1: Mike Mulugeta Suspect 2: Sunil Tripathi.”

With the story taking hold like wildfire, a number of people then went on to celebrate how social media had apparently found the suspect in the “white hat”. It was, said some, a victory for new media over the old school. All chose to ignore the fact that police had not named Mr Tripathi as a suspect. They also ignored the fact that he looked very little like the man being hunted by officers.

A forensic account of events by TheAtlantic.com website shows that not only had the internet sleuths failed to identify the suspect, they had also not bothered to check the source of the claim. An examination of the Boston Police department’s scanner for that evening reveals that Mr Tripathi’s name is not even mentioned by officers.

“By this time, there was a full-on frenzy as thousand upon thousands of tweets poured out, many celebrating new media’s victory in trouncing old media,” said The Atlantic. “It was all so shockingly new and the pitch was so high and it was so late at night on one of the craziest days in memory.”

The family of Sunil Tripathi became aware of the sinister twist to the Boston tragedy when they noticed a rapid increase on visits to the Facebook page and when people began posting messages. On Thursday evening they hurriedly took the site down but on other social media forums they monitored how their beloved Sunil was being accused of involvement in the most serious terror attack in the US since the events of 9/11.

For anywhere up to nine frenzied hours they felt utterly helpless. It was not until some time on Friday morning, when NBC reporter Pete Williams said on Twitter that Sunil Tripathi was not the man wanted by police, that the mayhem started to ease.

“The past 36 days had been so very difficult for us,” said Mr Tripathi’s sister. “And then the events of [those hours] were very trying.”

Some of those who posted erroneous speculation, including the former colleague from high school, have publicly apologised for their role in what subsequently transpired.

On Monday, Erik Martin, the general manager of Reddit, said in a web posting that the site had privately apologised to the family and was now also doing so publicly. “Though started with noble intentions, some of the activity on Reddit fuelled online witch hunts and dangerous speculation which spiralled into very negative consequences for innocent parties,” he said. “The Reddit staff and the millions of people on Reddit around the world deeply regret that this happened.”

The family of the 22-year-old student say they are trying to use the publicity generated by what happened to help their ongoing search. They have urged people to click on their Facebook page “Help Us Find Sunil Tripathi”.

On the site they are encouraging people to write a message of encouragement on their palm and then upload the image. They ask people to also spread the word across the state of Rhode Island and beyond about the young man who remains missing and to contact Providence police if someone has information they believe to be of value.

As for their experience with social media and the “disconnect” that may encourage people to post before thinking, Mr Tripathi’s sister said she hoped the lesson people would learn from this would be to treat each other “with care and delicacy”.

“We are a very fragile world right now and our family is very fragile,” she said. “We should all take care of one another.”

Viral infection: Tale of the wrong suspect

Thursday 18 April

Three days after the Boston Marathon bombings, a person who claims to have gone to high school with 22-year-old Sunil Tripathi, an undergraduate student at Brown University who has been missing more than a month, posts a message on popular social news website Reddit saying she thinks she recognises him from grainy surveillance photos of the finish line, close to where the two explosions took place.

A leading theory on Reddit’s ‘FirstBostonBombers’ thread, which was set up soon afterwards as a semi-organised crowd-sourced investigation, incorrectly identifies Sunil Tripathi as “the white hat suspect” and it begins to trend.

Friday 19 April

In the early hours of the morning, Twitter user named Greg Hughes tweets: “Boston Police Department has identified the names”. Sunil Tripathi is wrongly identified as “Suspect 2” from an audio tape of police scanner transmissions by social media commentators.

There is then a mass information cascade on Twitter and Reddit in which thousands of people name and re-tweet Sunil Tripathi as “Suspect 2”.

Between 3am and 4.30am, Mr Tripathi’s family receive 72 phone calls from media and social media asking for comment on his potential involvement in the case.

The Facebook page set up by Mr Tripathi’s family in an attempt to help find him is frozen due to abuse being posted on the page.

By dawn, Mr Tripathi’s name has circulated in the press in India and Britain. Soon afterwards, NBC confirms that two brothers, Tamerlan and Dzhokhar Tsarnaev, are in fact the primary suspects in the Boston bombing investigation.

Apologies are made by some people who re-tweeted Sunil Tripathi’s name and by the moderator of the Reddit threat ‘FirstBostonBombers’ to Sunil’s family.

Monday 22 April

Reddit issued a public apology for its coverage of the Boston bombings, admitting that it helped to fuel “online witch hunts”.

Hoax tweet of White House blast sends markets into a tailspin

Shortly after 1pm today, the Twitter feed for the Associated Press reported some shocking news: two explosions at The White House, and President Barack Obama injured. The news was promptly denied by Obama’s team, and disavowed by an AP editor, who took to Twitter to advise readers that the story was false, and that the agency’s Twitter feed had been hacked.

The reversal did not come quickly enough for the markets, however. In the moments between the fake tweet and its denial the Dow Jones industrial average dived 100 points. It recovered almost as quickly as White House press secretary Jay Carney assured reporters: “The President is fine.”

AP said it would suspend its Twitter account and the agency’s Mike Baker said, in a tweet, “the hack came less than an hour after some of us received an impressively disguised phishing email.” But AP is only the latest victim. CBS news Twitter accounts were hijacked last week by the Syrian Electronic Army, a pro-Assad group. And on 4 July, 2011, an imposter tweeted from Fox News, announcing that Obama had been assassinated.

Tim Walker