WASHINGTON >> A U.S. corporate security executive and former Marine who has been jailed in Moscow on spying charges has spent more than a decade cultivating friends and contacts in Russia, both virtual and real.

Paul Whelan sought out friends throughout the country, most often through a social networking site that is similar to Facebook and popular largely in Russia. Several told The Associated Press that the American never seemed sinister, merely someone who was interested in Russia and wanted to be pen pals.

“I know him as a friendly, polite, educated, and easygoing guy,” said one of his contacts, who, like the other Russians interviewed for this story, spoke on condition of anonymity because of Whelan’s legal troubles.

Whelan was arrested Dec. 28 while on a two-week visit to the country and has been charged with espionage. The Russian government has so far given no details about the allegations against him, but a close look at his social media history suggests why he might have come to the attention of the Russian security services, regardless of his motives.

He has collected dozens of contacts on the social media site, nearly all of them men, many of whom have at least some connection to the military.

His family back home says he was nothing more than a tourist. In a Washington Post op-ed published Friday, his twin brother, David, urged the U.S. government to pressure Russia to release him.

“Paul is a kind and considerate brother, son and uncle, and a generous and loyal friend,” he wrote. “He travels as often as he can, both for work and pleasure. He is many things to many people, but he is not a spy.”

Whelan, 48, could face up to 20 years in prison if convicted of spying. He is also a citizen of Britain, Canada and Ireland, which brings international pressure on Russia from several fronts. He was born in Canada to British parents, but grew up in Michigan, where he now lives.

His family said he was in Moscow over the holidays for the wedding of a fellow former Marine and had planned to travel to St. Petersburg before flying home this weekend. Instead he’s in Lefortovo, a notorious prison run by the KGB in Soviet times and still used for foreigners accused of spying.

Whelan has been visiting Russia since at least 2007, when he took advantage of a military program for Marines deployed in Iraq that gave them 15 days of leave and paid for the travel.

Even before then, he had begun developing a network of contacts throughout Russia. Some said they met him online in 2006 and became “pen pals,” trading practice in English for Russian. Whelan seemed fascinated with Russia and its culture, they said.

For nearly a decade, he has had an account on VKontakte, which means In Contact. Of his 58 friends at the time of his arrest, 54 were men. Many attended universities affiliated with the military, civil aviation or technical studies. Many share his interest in sports and firearms.

“We was guys with guns,” wrote another of his friends, who said he was a student working nights as a security guard when he first met Whalen online.

Both men, who live in separate Russian cities far from Moscow, said they first met Whelan in person in 2008 when he traveled around the country to meet some of his new friends. Others said they have only communicated online.

Whelan’s brother said it would not be surprising to find Russian soldiers among his contacts.

“I’m pretty sure that some of the people he knows through social media are probably Russian soldiers because there are a lot of Russian soldiers and he probably knows one,” David Whelan said in an interview.

One of Paul Whelan’s friends on VKontakte said he believed the arrest was a mistake because a true spy would never act as openly as he did. He said Whelan gave him his home address and they exchanged Christmas cards.

Former CIA officers also have expressed doubts that Whelan was working for U.S. intelligence. They note that the CIA would be unlikely to use someone in Russia without diplomatic immunity and leave them vulnerable to arrest.

Whelan’s Marine record also would likely prevent U.S. intelligence from hiring him. He began active duty with the Marines in 2003 and was deployed twice to Iraq, rising to staff sergeant. But his military career ended with a court martial in 2008, when he was convicted on charges that included attempted larceny and dereliction of duty.

Court documents released by the military show he was accused of attempting to steal more than $10,000 while on duty in Iraq, where he worked as a clerk, in September 2006. He was also convicted of using a false social security number and profile for a military computer system to grade his own examinations, and of writing 10 bad checks totaling around $6,000.

He was dropped two grades in rank and given a bad conduct discharge from the Marine Corps.

“This guy is not an intel asset,” said Malcom Nance, a veteran intelligence officer. “He’s not the type of person you would use as an asset. There is no way.”

Nance said he suspects Russian intelligence officers have been watching Whelan for years, wondering if they could use him in some way and maybe trying to flip him.

A member of Russia’s parliament suggested Friday that once the investigation into Whelan was completed, he could be swapped for Maria Butina, a Russian woman jailed in the U.S. since July. She pleaded guilty last month to conspiring to act as a foreign agent by trying to infiltrate conservative circles and the National Rifle Association to influence U.S. politics.

However, she has been cooperating with federal prosecutors and is unlikely to spend too much time behind bars. Federal sentencing guidelines call for no jail time to six months.

After his discharge, Whelan returned to his job in the temporary staffing company Kelly Services, based in Troy, Michigan, where he had worked since 2001 in the IT department until taking the leave of military absence. He was Kelly’s head of global security and investigations until 2016.

Early the following year, Whelan joined auto parts supplier BorgWarner as global security director. BorgWarner, based in Auburn Hills, Michigan, has facilities around the world but none in Russia and he never traveled to the country for business, company spokeswoman Kathy Graham said.