Former Navy SEAL Glen Doherty was one of the four Americans killed by protesters at the US Consulate, in Benghazi, Libya on Tuesday, the anniversary of 9/11.

Doherty (42) from Winchester, Massachusetts, was working as a security officer to protect the US Ambassador Christopher J Stevens. Having moved from Massachusetts, Doherty was living in California and working for a private security contractor for the US government when the group of armed militants attacked the consulate.

His sister Kate Quigley, from Marblehead, told the Boston Herald “He lived his life to the fullest, and he always did everything he wanted to do…Even though he stood 5-10, he was always the biggest person in the room.

“Glen was unconventional. He wants us to celebrate his life, and that’s what we’ll do. ... He’s a hero.”

Doherty, Stevens, Foreign Service Officer Sean Smith and one other were killed in the violence. Although initially the authorities believed the protest was against Sam Bacile’s movie “Innocence of Muslims” which calls Islam “a cancer”. However investigations are ongoing and there has been some speculation over whether the protest was a premeditated act of terrorism.

Quigley continued “My take is I know he died protecting America and he died trying to help anybody who got hurt that day.

“To be honest with you, Glen was so good at what he did, I don’t think he went down to a couple protesters over a video. But whether it was a video or a bigger thing, I don’t know. I know he died protecting this country.”

Prior to working for the private security company Doherty was a Navy SEAL for eight years.

“We all knew the risk, but he’s come back time and time again,” Quigley said.

”He was really good at what he did. He was a sniper. He was in Iraq when the palaces came down after Saddam Hussein.”

Doherty graduated from Winchester High in 1988 and went to flight school at Embry-Riddle Aeronautical University in Arizona. He then moved to Utah and worked as a professional skier becoming a Navy SEAL.

Having been a SEAL for eight years he became an author, writing the book “The 21st Century Sniper” with Brandon Webb. He also appeared in a documentary about snipers and a reality show about hunting terrorists called “The Wanted.”

The former SEAL’s ex-wife Sonja Johnson, said her high school sweetheart was “brave” and the “best of the best”.

“It’s hard to get your head around,” Johnson said.

“We just never thought this would happen to Glen. He was the best, he was the smartest, and it’s very tragic. We all have personal stories, whether it was the war in Iraq or Afghanistan. It really hits home. It really puts a face on the terrible things that are happening in the world today.”

CBS reports that the FBI has opened an investigation in the men’s deaths. The Obama administration believes that the attack was perpetrated by well-armed thugs.