Never before seen images show the failed ISIS assault that led to the death of a US Navy SEAL

It had been relatively quiet for a month when in the morning of May 3, 2016, one of the largest assaults from Islamic State militants began.

Over 120 ISIS fighters, 20 armored vehicles equipped with crew-served weapons, and at least one bulldozer attempted to push into Tel Askuf, a once predominately Christian city, about 20 miles north of the ISIS-held Mosul.

In their minds, the jihadists had good reason for their surprise attack: according to Kurdish sources, within the town's walls was a handful of US advisors who had been assisting the local Kurdish Peshmerga forces along with the Asayish, a Kurdish security and intelligence agency, and several Christian militiamen.

After about 20 minutes, ISIS fighters managed to punch through the Peshmerga front lines and advance toward Tel Askuf. When the US advisors in the town finally made contact with ISIS forces, the area's Quick Reaction Force (QRF) was called, and around 20 Navy SEALs arrived with weapons at-the-ready.

However, about 2-hours in, one of the QRF members, Naval Special Warfare Operator 1st Class Charles Keating IV, was hit by small arms fire after climbing to a roof to pick off ISIS militants. A Black Hawk medevac was called in to evacuate the wounded, but Keating's injuries proved to be fatal.

The ensuing battle was so fierce that additional aerial support was required - A-10s, F-15s, F-16s, B-52s, and drones were all scrambled to assist the ground forces. Ultimately, ISIS was forced back from Tel Askuf.

Keating, 31, an Arizona native, was posthumously promoted to Chief Petty Officer.

"This was a large fight, there's [no] question about it," explained Colonel Steve Warren, a spokesman for the US Department of Defense.

Though media coverage has centered around the scenes in Tel Askuf, Business Insider obtained new footage from a Peshmerga soldier who claimed to be on the front lines against the initial ISIS assault. The images that follow not only depict the chaos and fear from ISIS' attack on the front lines, but the dangers that US medevac helicopters face to ensure a servicemember receives medical care.

We have turned the footage into a series of stills below.

Warning: The following images may be graphic to some.