(CNN) -- Fourteen times in nine years, Sgt. 1st Class Kristoffer Domeij had left his family behind and headed out on deployment as an Army Ranger, taking part in hundreds of combat missions in Iraq and Afghanistan, all before his 30th birthday.





His most recent tour turned out to be his last.





The veteran soldier's death rattled his commanders, as well as those in his native San Diego. His former football coach, Jeff Carpenter, remembered Domeij as diligent, funny, passionate and team-oriented.





"I told my classes that I was incredibly sad to begin with and incredibly angry," said Carpenter, who besides being an assistant coach the past 18 years is also a social sciences teacher at Rancho Bernardo High School. "Just the fact that it happened to someone like him -- it's hard."





Domeij, 1st Lt. Ashley White and Pvt. 1st Class Christopher Horns all died Saturday in Kandahar province when an improvised explosive device blew up near their assault force, according to a U.S. Army Special Operations Command news release.





The trio's death is far from unprecedented: According to CNN's count, based on U.S. military reports, there have been 1,811 U.S. troops killed during Operation Enduring Freedom, the U.S.-led mission in Afghanistan that began in October 2001.





Each person, each death, is unique. In Domeij's case, that translates to a man whom his unit commander described as "irreplaceable" -- on the battlefield and in life.





"He was one of those men who known by all as much for his humor, enthusiasm and loyal friendship as he was for his unparalleled skill and bravery under fire," said Lt. Col. David Hodne, head of the 75th Ranger Regiment's 2nd battalion. "This was a Ranger you wanted at your side when the chips were down."





Domeij distinguished himself as a person as much as he did as a player while in high school, his former coach recalled.





"He was just a great kid," Carpenter said, describing his great sense of humor and engaging personality. "And we knew, as coaches, that no matter what, this was a kid who was going to play hard and (all) out."





Carpenter said he wasn't surprised when Domeij told him he was going to enlist. "It made all the sense in the world," the coach said, given Domeij's proven dedication to and ability to thrive as a member of a team.





So Domeij joined the Army in July, a few months after graduating high school and not long before the September 11 terrorist attacks. Nine months later, he became part of the Ranger regiment.





Domeij was based at that unit's headquarters at Joint Base Lewis-McChord in Washington state, where his role was as a joint terminal attack controller. The person in this position often advances into harm's way, directing allied combat aircraft on where and when to strike.





His regiment's commander, Col. Mark Odom, called Domeij "technically and tactically competent" as well as critically important.





"His ability to employ fire support platforms made him a game-changer on the battlefield -- an operator who, in real terms, had the value of an entire strike force on the battlefield," Odom said in the news release.





The military culture is very much ingrained in the Southern California culture in which Domeij grew up. Much of the Pacific fleet is based there at U.S. Naval Base San Diego. A large Marine base at Camp Pendleton is about 30 miles northwest of Rancho Bernardo High, with the famed Marine Corps Air Station Miramar about 11 miles south.





The parents of many of that high school's students -- whose enrollment was about 3,000 when Domeij attended -- are in the military, Carpenter notes. Yet while multiple students enlist each year, Domeij's death is the first his coach can recall since Rancho Bernardo opened in 1990.





Carpenter said he'd kept in touch with his former player since graduation, knowing full well that was in Special Operations and in harm's way. But he said neither
What did the coach say? In which province was Doemij killed? What has been hard on the community? When did Domeij join the army? Where was Domeij killed? When did he join? Where was he killed?
"I told my classes that I was incredibly sad to begin with and incredibly angry," Kandahar Domeij's death July, Kandahar province July, Kandahar province
question: What did the coach say?, answer: "I told my classes that I was incredibly sad to begin with and incredibly angry," | question: In which province was Doemij killed?, answer: Kandahar | question: What has been hard on the community?, answer: Domeij's death | question: When did Domeij join the army?, answer: July, | question: Where was Domeij killed?, answer: Kandahar province | question: When did he join?, answer: July, | question: Where was he killed?, answer: Kandahar province