By Felicia Schwartz And Natalie Andrews 

WASHINGTON--An American citizen who left the U.S. this year to fight with Islamic State militants in Syria was shot dead during a battle with rival Syria opposition fighters late last week in Aleppo, according to the Obama administration and a Syrian opposition official.

The incident served to underscore concerns expressed in recent days by administration officials over the threat posed by Islamist fighters from the U.S. and West who have passports that could allow them to return home to carry out domestic terror attacks.

"The piece that we're very concerned about now...is the threat of foreign fighters who have Western passports, and that's a piece that we're tracking closely as well because we think it could pose a threat to us," State Department spokeswoman Jen Psaki said Tuesday.

Douglas McCain, 33 years old, traveled overseas this year before entering Syria, said Michael Roland, a cousin.

The Syrian opposition official said Mr. McCain was fighting with the group calling itself the Islamic State in the northern Aleppo countryside when he was killed.

An American passport found on his body was issued in November 2013, according to a photograph provided by a Syrian opposition official to The Wall Street Journal. Mr. McCain died wearing military-style camouflage and a flak vest with ammunition pouches. His body had gaping bullet wounds in the head, jaw and leg, the photo, provided by the same official, shows.

Mr. McCain was born in Illinois and attended high school in the Minneapolis area, according to public records. He later moved to San Diego, where he has relatives, and was a student at San Diego City College. His mother remains in Minneapolis, Mr. Roland said.

Many of Mr. McCain's family members were stunned to learn about his ties to the Islamic State, Mr. Roland said. "This is like, 'Are you serious?' This is not the kid that I knew of," he said.

Mr. McCain's mother was informed of his death by U.S. government officials on Monday, Mr. Roland said. The State Department is in contact with his family and is providing consular assistance, Ms. Psaki said.

The U.S. has no evidence that the Islamic State is planning to carry out 9/11-style attacks, but has been monitoring the group's capabilities for signs that it could shift tactics.

The State Department estimates that 12,000 foreign fighters from over 50 countries have gone to fight in Syria. Americans likely make up only a very small portion of this group, experts say.

U.K. officials now believe about 500 British citizens have gone to Syria to fight with terrorist groups and that about half have come back, a British security official said.

A National Security Council official said the government knew that Mr. McCain was in Syria.

President Barack Obama is chairing a meeting of the United Nations General Assembly in September to discuss the threat of terrorism and foreign fighters.

"The issue of foreign fighters and the concern of individuals with Western passports or passports that would enable them to travel into countries where they can do harm is certainly at the top of our agenda and the top of the agenda of many countries," Ms. Psaki said.

The Pentagon also expressed concerns about foreign fighters in Syria on Tuesday.

"And you don't need to look any further than the recruitment of foreign fighters and the degree to which not just the United States government, but many Western governments are concerned about these foreign fighters leaving their shores, going over there, getting radicalized, trained and then coming back and executing attacks, which is not out of the realm of the possible," Pentagon spokesman Rear Adm. John Kirby said.

Mr. McCain, who Mr. Roland said converted to Islam a number of years ago, was active on Facebook under the name "Duale ThaslaveofAllah." On Mr. McCain's Facebook page, he said he worked for "Dawah -- Calling to Allah, " a page inviting people to join Islam.

He regularly tweeted about Islam, under the handle @IamtheTooth. "I reverted to Islam 10 years ago and I must say In-sha-Allah I will never look back the best thing that ever happen to me," he tweeted in June.

Mr. McCain's Facebook page was briefly updated Tuesday with a new profile picture of a child crying. A few hours later, the page was deactivated.

As news of his death spread, several family members expressed shock and disbelief on Facebook. They later declined to comment or couldn't be reached.

His sister, Lisa Roland, posted a message saying: "I won't ask God why, but it hurts. My heart is heavy and my tears are because I don't understand."

Another sister, Delecia McCain, called her brother's death "unreal" on a Facebook posting, adding: "I really don't understand why and how and I have no words."

Lisa Schwartz

, Adam Entous, John R. Emshwiller and Siobhan Gorman contributed to this article.

Subscribe to WSJ: http://online.wsj.com?mod=djnwires

Meta Platforms (NASDAQ:META)
Historical Stock Chart
From Feb 2024 to Mar 2024 Click Here for more Meta Platforms Charts.
Meta Platforms (NASDAQ:META)
Historical Stock Chart
From Mar 2023 to Mar 2024 Click Here for more Meta Platforms Charts.