By George P. Hassett

Somerville police patrolled the world of cyberspace this week, investigating Craigslist ads and MySpace pages to catch a man allegedly responsible for an armed robbery on the city’s bike path.

The stick-up victim monitored Craigslist postings looking for the cell phone that had been stolen from him Sunday Sept. 16 as he passed Lexington Park and was robbed by two young black men, police said. He came across a phone just like his and the location was in Somerville, police said. Police regularly monitor Web sites such as Craigslist, hoping to find items taken in recent thefts and robberies, according to Somerville investigators.

Working with police investigators, the victim set up an e-mail account under the false name of Steven Villard and contacted the person selling the phone, police said. A link to the seller’s MySpace page came up and as the pictures were downloading, the victim recognized one of the men who had robbed him at knife point, Casey Kolenda, 21, of 62 Hinckley St., police said.

The victim informed Somerville police detectives Michael Kiely and Mario Oliveira of what he had learned. Oliveira called a phone number he got from Kolenda when Kolenda believed he was selling the phone to Steven Villard and arranged to purchase the phone at the Porter Square MBTA station for $300, police said. At the station, Kiely played the role of buyer Steve Villard and approached Kolenda, who he recognized from the MySpace pictures, sitting with three other men, police said.

After a short conversation, Kiely took the phone and watched as Kolenda elbowed one of the men at his side, Brandon Sheffield, 20, of 132 Central St., in what detectives believe was a signal, police said. However, before Kolenda and Sheffield could move, Kiely gave a signal of his own and an arrest team took the suspects to the ground for the officers safety, police said.

Kolenda was arrested and charged with armed robbery and receiving stolen property worth more than $250, Sheffield was arrested and charged with receiving stolen property worth more than $250 and a third man, Frankey Anfield, 19, no address, was arrested and charged with receiving stolen property more than $250.

The victim later confirmed to detectives the serial number of his stolen phone matched the serial number of the phone Kolenda had been trying to sell online, police said.