John Bacon and Doug Stanglin

USA TODAY

An American who lived in Minnesota and San Diego was killed in Syria, where he had gone to fight alongside terrorists, officials say.

A national security spokeswoman at the White House, Caitlin Hayden, confirmed the death of Douglas McCain, 33, and said Tuesday that U.S. officials had been aware of his presence in Syria.

McCain had traveled to Syria to join a militant group, believed to be the Islamic State, Associated Press reported, citing a U.S. official who declined to be identified by name and spoke only on condition of anonymity.

"We were aware of U.S. Citizen Douglas McAuthur McCain's presence in Syria and can confirm his death,'' Hayden said. "We continue to use every tool we possess to disrupt and dissuade individuals from traveling abroad for violent jihad and to track and engage those who return."

NBC News, in first reporting the death, said it had seen photos of McCain's body, including a distinctive neck tattoo, and U.S. passport.

A relative, Kenneth McCain, said the State Department had called his family to report that Douglas McCain had been killed in Syria, AP reported.

Kenyata McCain, a cousin, said Tuesday that Douglas McCain's mother received a call Monday from the State Department reporting that her son was killed over the weekend in Syria, the Minneapolis Star Tribune reported online.

McCain ad lived in San Diego in recent years and was a 1999 graduate of Robbinsdale Cooper High School in Minnespota, said the cousins, who both live in the Twin Cities and are roughly his age, StarTribune.com reported.

Kenyata McCain said she was in touch with Douglas McCain as recently as Friday, and "he was telling all of us he was in Turkey."

"I know that he had strong Muslim beliefs," she said, "but I didn't know that he was in support of ISIS. I didn't think he would be."

NBC cited an activist linked to the Free Syrian Army who saw the photos and said McCain was among three foreigners fighting with Islamic State who died in Syria.

CNN reported that McCain's uncle, Ken McCain, said the State Department informed the family Monday of McCain's death.

Ken McCain told CNN the family was "devastated" and "just as surprised as the country" to learn of his nephew's participation with IS. Ken McCain said his nephew converted from Christianity to Islam several years ago.

Islamic State, also called ISIS or ISIL, is waging a war aimed at building an arch-conservative Sunni state across a swath of Syria and Iraq. The group made global news last week with a video showing the beheading of American photojournalist James Foley.

President Obama then urged Muslim nations to band together to stop the Islamic State.

The Facebook page NBC says is McCain's indicated he went to Robbinsdale Cooper High School in New Hope, Minn. McCain was born in Chicago and worked in San Diego for "Dawah -- Calling to Allah," which describes itself as a non-profit dedicated to spreading the word about Islam and inviting people to join the faith.

He lists as a recently added friend Abu Qaqa Al Malayzi, whose own Facebook page says he works for the Islamic State and currently lives in Raqqah, Syria, the current headquarters of IS. Al Malayzi changed his profile photo Aug. 22 to a photo wearing a mask and cradling an AK-47.

There are many posters on McCain's own Facebook photo page with a Muslim theme, including an "I (heart) Allah." Another is called "Soldiers of Allah" and shows what appear to be desert warriors striding toward the light under the headline "They are coming back."

There are also playful entries on his Facebook page, noting that he is a fan of both the Chicago Bulls and comedian Dave Chapelle.

Much of the information on the Facebook page was stripped away sometime Wednesday.

Contributing: Oren Dorell; William M. Welch in Los Angeles