The 2008 Radnor High School graduate was last seen March 16 by his Brown University-area housemates who told police Tripathi was around that Saturday morning.
At some point, the 22-year-old Bryn Mawr native walked out of his room leaving behind his wallet, credit cards, cell phone, and what has been described as a vaguely worded note.
When his close friends were unable to reach Tripathi, they contacted police to report him missing.
In the last two weeks numerous law-enforcement investigators, family and friends have searched coffee shops, homeless shelters, soup kitchens, hospitals and morgues. They have visited stores, neighborhoods, and hiked along Providence rivers at low tide.
"Every ounce of property within walking distance - a 3-mile radius - had been covered," said Sacco. Foul play is not suspected. Sacco would not reveal the contents of the note found in Tripathi's room.
An FBI forensic analysis of his computer, bank, and phone turned up no clues to his whereabouts.
A surveillance video taken the night before he disappeared from a nearby business recently surfaced. It shows a man fitting the description of the lanky 6-foot, 130-pound Tripathi walking in his neighborhood. Police haven not been able to say definitively it is the missing man, but the footage has encouraged the family.
"I do believe it is him," said Ravi Tripathi, 26, the missing man's brother. The close-knit family has traveled to Rhode Island, and the video, he said, has given them information to use in their search.
"Sunny" as he is known, had taken a leave from Brown University where he was studying philosophy. He was volunteering at a local library while deciding his next steps, Ravi Tripathi said.
His brother, who suffers from depression, was in constant contact with his family through calls, Facebook, or texts, he said. They last heard from him the night before he disappeared.
The "Help Us Find Sunil Tripathi" Facebook page has helped drive national attention to the case. It generated more than 1.2 million unique views in its first week, and, as of Friday, had more than 4,400 followers.
Volunteers plastered posters around Providence and at Philadelphia's 30th Street Station and at regional-rail stations. The calls and tips have come in from South Carolina, Connecticut, Pennsylvania, Boston and, of course, Rhode Island.
"It is social media that has taken [the exposure] to the next level," said Sacco. He said the exposure has gone beyond what his department could do.
Sacco asks that any persons who believe they have seen Sunil Tripathi contact their local police departments, who will be able to assist in tracking down any evidence, such as nearby surveillance video.
Contact Mari A. Schaefer at 610-313-8111, email@example.com, or follow @MariSchaefer on Twitter.