(CNN) When a team of less than a dozen U.S. military advisers came under attack in Iraq Tuesday from more than 100 ISIS fighters, Navy SEAL Charles Keating IV was part of the force sent in to rescue them.

All the advisers made it back. Keating, a decorated combat veteran and star athlete who decided to enlist after the 9/11 attacks, did not.

Providing new details Wednesday about the operation that took the life of the grandson of prominent financier and World War II pilot Charles Keating Jr., Coalition spokesman Col. Steve Warren said that the clash between ISIS and the Kurdish Peshmerga forces the advisers were assisting was "a big fight, one of the largest we've seen recently."

Keating's death is the third American combat loss since the U.S. redeployed forces to Iraq in the summer of 2014 to advise local forces and conduct Special Operations missions against ISIS. The 31-year-old Special Warfare Operator 1st Class was on his third tour in Iraq.

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Ash Carter: We want to accelerate campaign against ISIS 09:28

Ash Carter: We want to accelerate campaign against ISIS

ISIS was attempting to capture the Iraqi town of Telskof from the Kurdish forces -- about 3 miles from ISIS' frontline -- unaware that U.S. troops were in the area, according to Warren. ISIS managed to assemble about 125 fighters and 20 vehicles for the assault, destroying a Peshmerga checkpoint as they crossed the frontline and engaged Kurdish troops for more than 12 hours.

"The enemy was able to very covertly assemble enough force, which included the several truck bombs, some bulldozers, and of course their infantry. And they were available to punch through the Kurdish line there" and "sprint" towards their objective, Warren said.

Warren said that the Quick Reaction Force, of which Keating was a part, was able to evacuate the advisers "relatively rapidly within the first couple of hours." But it was during this operation, he noted, that Keating was struck by "direct fire" at 9:32 a.m local time.

Two medical evacuation helicopters were called and able to evacuate Keating -- despite sustaining small-arms fire from ISIS themselves -- within an hour of his being hit, but "his wound was not survivable," Warren said.

Coalition air support including F-15s, A-10s, B-52s and drones also responded to the ISIS offensive by launching 31 strikes, destroying 20 enemy vehicles and killing 58 ISIS fighters, Warren said.

The Peshmerga have since regained control of the town, he added.

Defense Secretary cites 'heroic' actions

Defense Secretary Ash Carter told CNN's Christiane Amanpour in Germany that Keating's death was "tragic" and called his actions "heroic."

He added that Keating's death "shows us this is a risky campaign. .... We will defeat ISIL but there is risk associated with it."

Keating's relatives also used the word hero to describe the fallen soldier.

"He is our family hero in every sense of the word," cousin Elizabeth Ann Keating told CNN.

Keating enlisted in the Navy in February 2007 and graduated from Basic Underwater Demolition/SEAL training in 2008, the Pentagon said in a statement confirming Keating's death.

The Pentagon said he had previously been deployed to Afghanistan and this marked his third tour of Iraq.

Keating had earned numerous awards and decorations including the Bronze Star Medal with Combat "V."

He came from a long line of devoted service members, going back to his namesake, great-grandfather Charles Keating, who served in World War I, and grandfather, Charles Keating Jr., a naval pilot in World War II.

Charles Jr. rose to prominence in the mid-20th century as a lawyer and businessman who made millions in Phoenix real estate before he was implicated in the $150 billion savings-and-loan crisis that fleeced thousands of depositors with the help of U.S. senators. He always insisted he'd done nothing wrong and served time for fraud, racketeering and conspiracy. The verdicts were later overturned and he pleaded guilty on lesser charges. He died in 2014 at age 90.

U.S. Sen. John McCain of Arizona, who was implicated in the scandal as a member of the Keating Five but was later cleared of wrongdoing, and daughter Meghan McCain sent their condolences to the family.

This is tragic news. Pray for the entire Keating Family with the loss of Arizonan Charlie Keating IV killed in Iraq https://t.co/gvfVnqgUSD — Meghan McCain (@MeghanMcCain) May 4, 2016

"I send my deepest prayers and condolences to the family and loved ones of Charlie Keating who was tragically killed in action fighting ISIL in Iraq," McCain said in a statement, using a different name for ISIS. "Like so many brave Americans who came before him, Charlie sacrificed his life in honorable service to our nation for a cause greater than self-interest, which we can never truly repay."

Keating's distinguished track performance

Keating was mourned in his home state of Arizona and beyond as a star athlete whose transition to military service came as little surprise to those who knew him. Gov. Doug Ducey ordered flags in the state to be lowered to half-staff on Wednesday in his honor.

A 2004 graduate of Arcadia High School in Phoenix, he was city and region champion in the 1,600-meter run as a sophomore, junior and senior, according to Azcentral.com. At Indiana University, he was a member of the 2004-05 track team that finished as a Big Ten runner-up in both the indoor and outdoor seasons, competing in the mile run, the school said in a statement.

His high school track and cross country coach, Robert Wayne Reniewicki, said Keating made the decision to serve his country after the September 11, 2001, terrorist attacks.

"It didn't surprise me when he said (he) wanted to be a Navy SEAL," Reniewicki told CNN.

He said the attacks happened while Keating and his teammates were on a run during his sophomore year and made an impact.

"You could tell he was a guy who wanted to be the best and find out what he was made of, and serving as special operations forces for his country embodied that," Robert Chapman, professor of kinesiology at IU Bloomington and men's cross country coach from 1998 to 2007, said in a statement.

Keating's father, IU alumnus Charles H. Keating III, was a three-time All-American for the Hoosiers in the breaststroke and a four-time Big Ten Champion. Keating III finished fifth in the breaststroke at the 1976 Olympics in Montreal, the school said.

"Charlie Keating was a valuable member of the Indiana Athletics community. His father was a decorated All-American and Olympian for the Hoosiers, and their family gave me one of my first coaching jobs in Phoenix," Indiana head swimming and diving coach Ray Looze said. "On behalf of the IU Swimming community, we express our deepest condolences."

White House Press Secretary Josh Earnest said President Barack Obama was briefed on the death.

"Everyone extends condolences to the family of the service member that was killed today in northern Iraq," Earnest said at his daily briefing with reporters, adding that it's a reminder of the risks Americans continue to face even in advisory roles there.