BOSTON (CBS) – A former Navy SEAL from Winchester was one of four Americans who died in the attack on the U.S. consulate in Libya Wednesday.

Forty-two-year-old Glen Doherty was killed with U.S. Ambassador John Christopher Stevens in Benghazi, Doherty’s family confirmed Thursday.

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WBZ NewsRadio 1030’s Ben Parker reports

The former Navy Seal was working for a private security company in Benghazi when Muslim extremists attacked the U.S. Consulate in Libya on Tuesday, killing him, two other Americans, and U.S. Ambassador Chris Stevens.

Doherty was a 1988 graduate of Winchester High School, where he was on the tennis and wrestling teams.  He was single and had no children.

It surprises no one who knew him as a teenager that Winchester native Glen Doherty would grow up to do great things.

“Glen lived his life to the fullest,” explained his sister Kate Quigley. “He was my brother but if you asked his friends, he was their brother as well.”

His mother lives in Woburn and family friends have been visiting the home all day.

“He was my brother, but if you asked his friends they would say he was their brother too,” Kate Quigley said in a brief statement to reporters outside the house Thursday afternoon.

She thanked everyone for their support and asked for the family’s privacy at this time.

“Glen was bursting with life. Every day his huge smile and his happy-go-lucky optimism filled my classroom. He got along with all types of people, was a class leader and, from the perspective of thirty years of teaching, one of my most memorable students,” Judy Hession, Doherty’s 11th grade English teacher, said in a statement.

All flags in Winchester will be flown at half staff in his memory.

“My thoughts and concerns go out to his family,” Gov. Deval Patrick said.  “I hope they know that if there’s anything we can do to comfort them and to help them through these very difficult coming days, we’re here for them.”

“Glen served our country heroically, and words cannot express our sadness for his family or our gratitude for their sacrifice,” Sen. Scott Brown said in a statement Thursday afternoon.

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Doherty co-wrote a book in 2010 with fellow Navy SEAL Brandon Webb titled “Navy SEAL Sniper: An Intimate Look at the Sniper of the 21st Century.”

According to the book, Doherty was “a combat-decorated SEAL who served in the U.S. Navy for nine years.”

A third victim in the attacks has been identified as Foreign Service Officer Sean Smith.

The identity of the fourth American killed is still not known.

The violence in Libya actually began in Cairo, Egypt, where it continued on Thursday, triggered by an internet video made in America that Muslims believe disrespects the prophet Mohammed.

Sources told CBS News that terrorists may have used the demonstration outside the consulate as a cover to get inside and then strike and that it may be linked to Tuesday’s anniversary of the 9/11 terror attacks.

Attacks on U.S. targets are also spreading throughout the Muslim world.

On Thursday, mobs also attacked the U.S. Embassy in Yemen, which was once home to former United States Ambassador Charles Dunbar – now a professor of International Relations at Boston University.

“I would have expected an explosive reaction from the Yemenis,” Ambassador Dunbar said. “And I expect that will continue.”

Dunbar also served as U.S. Ambassador to Qatar and to Afghanistan, but was U.S. Ambassador to Yemen during the first Gulf War. At the time, he remembers, his safety was always a worry.

“Sure you’re concerned about [your safety as the Ambassador], but at the same time, you recognize that there is risk in the job,” according to Dunbar.

Dunbar says Ambassador Stevens was a role model for everyone in foreign service. He warns, too, that the danger continues.

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“American diplomats, like the military, are in harm’s way”especially as negative reaction to this video continues to intensify, said Dunbar. “My hope, not my suspicion, is that it will pass [but] I don’t think it’s going to go away overnight.”

WBZ-TV’s Jim Armstrong contributed to this report.