An American service member was killed in Iraq Tuesday as the U.S. military stepped up its role helping Christian and Kurdish militias battling ISIS near the terror group's stronghold in Mosul.

He has been identified as 31-year-old Charlie Keating IV.

Thirty-one-year-old Charlie Keating IV. via Facebook

Keating, 31, attended the Naval Academy before becoming a Navy SEAL based out of San Diego, California.

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A 2004 graduate of Phoenix's Arcadia High School, Keating was city and region champion in the 1,600-meter run as a sophomore, junior and senior.

Keating was planning to get married in November, his former high school track coach said.

Keating earned all-city and first-team all-state honors as a senior, according to Indiana University, where he ran cross country and track on scholarship.

"It is a combat death, of course. And a very sad loss," U.S. Secretary of Defense Ash Carter said in Stuttgart, Germany, where he was meeting NATO allies.

The casualty was confirmed as a Navy SEAL, CBS News national security correspondent David Martin reports. There are 30 SEALs in Iraq as part of a Special Forces advise and assist mission.

The death occurred "in the neighborhood of Erbil," the capital of Iraq's semi-autonomous Kurdistan region, according to Carter. Martin reports the battle was north of Mosul, an area that saw intense fighting Tuesday as ISIS militants tried to fight their way north from their stronghold.

The U.S.-led "Operation Inherent Resolve" issued a short written statement saying a coalition "service member was killed in northern Iraq as a result of enemy fire."

Martin reports the deceased SEAP was an American adviser to the Kurdish Peshmerga force. He was working with a Peshmerga unit two to three miles behind the front line during a battle with ISIS when some of the militants managed to get into a Peshmerga camp in Kurdish territory to kill the American with gun fire.

"It was a real battle, not just one-off raid," reports Martin.

An image taken from video posted online by ISIS purportedly shows one of the group's militants firing on a Kurdish Peshermga position during an intense battle north of Mosul, Iraq, May 3, 2016.

ISIS forces broke through using three truck bombs followed by bulldozers which cleared the wreckage away, which is how they got in the rear. They had two more truck bombs with them but they were destroyed by air strikes, Martin reports.

U.S. advisers rotate from camp to camp - so U.S. Navy SEALS just happened to be at that camp when the attack came, Martin said.

A senior U.S. military official told CBS News that American F-15 fighter jets and drones provided air support -- 23 strikes in all -- to the Peshmerga forces during what was described as an intense battle. There were no other U.S. casualties reported during the battle. Casualties among the Peshmerga remained unclear.

Earlier Tuesday it was widely reported that U.S. and coalition aircraft were supporting forces battling the Islamic State of Iraq and Syria (ISIS) north of Mosul. Mosul is approximately 50 miles west of Erbil.

ISIS militants advanced north from Mosul Tuesday morning in an apparent attempt to win new ground after a series of battlefield losses in both Iraq and neighboring Syria. The fighters briefly took control of the Christian town of Teleskof before reportedly being pushed out by local militias -- with the help of U.S. and coalition air support.

Tuesday's fatality was the second for the U.S. military this year in Iraq. A U.S. Marine was killed and several more were wounded by enemy rocket fire in northern Iraq in mid-March.

ISIS rockets fired at the site of a new training base for the Iraqi army in Makmour were blamed for the March death.

CBS News/ISW

The U.S.-led coalition's efforts to shore-up Iraqi forces in Makmour in preparation for an expected assault on Mosul has brought a spike in attacks, American officials said in March. The training base in Makmour sits between Mosul and Erbil, to the south.

Defense officials say it is not unusual for advisers to be operating within a couple miles of the front lines. So this was just another day in the life of an American adviser -- until it turned deadly, Martin reports.

The last U.S. service member to be killed in Iraq prior to the March death was in October 2015.