It was confusing and horrific. Amongst the chaos and carnage of the battle for Mosul, we came across a scene so sad it's seared into my mind's eye forever.

We were in a small tent in a refugee camp, 20 kilometres outside of Mosul.

I'd been told that ambulances ferried people here from the front lines, and wanted to gauge the impact the battle was having on civilians.

We entered to find no real facilities. It was more like a way station. There was almost no-one around. As we waited for a medic to finish talking to someone else my eye was drawn to two little figures lying on the ground.

I was thrown off balance. I was still looking for signs of doctors at work but could see none. I could hear crying but could see no movement. A little girl lay staring up at the ceiling.

As I gazed into her eyes, trying to understand what I was seeing, I slowly began to realise there was no life there, no sparkle, no anguish.

I've seen children maimed by shrapnel from artillery, and pulled from the rubble of an earthquake, but this was something else. Shocking because it was so unexpected.

The medic swung around. I asked Middle East cameraman Aaron Hollett to roll. And we captured a moment that reflects the grim reality of war.

It's distressing, but too often hidden from view.

The medic, Fathi, told us the girl was dead. As he closed her two, unseeing eyes, I couldn't help think of my own little girl going to school back in Beirut.

Little Dunya Uday might have been the same age, it was hard to tell. It looked to my untrained eye like she'd been suffering malnutrition and dehydration.

For me, in moments like this, it's as if a trap door opens and your inner self falls into the darkness.

A professional shell takes over, keeping it going in the face of an outrage that challenges your very soul: the death of a little girl, wrapped in thermal foil, whose immobile face had a whole life of loving and crying yet to give.

Dunya Uday died of a penetrating head wound: shrapnel from a mortar that exploded near her home.

I don't know who fired the mortar. But IS had already been forced out, government troops had moved in and IS has no qualms about firing back into the neighbourhoods it once occupied.

Fathi was outraged he couldn't get an ambulance to speed her into the Emergency Hospital in Erbil and broke down as I spoke to him.

I had no way to know if she could have been saved. But this and other experiences made it clear to me that, for all the months of planning the battle for Mosul, the authorities had failed to plan for adequate medical care for civilians.

Throughout it all, her brother Mohamed lay crying on the ground beside her.

He was eventually carried to a crowded ambulance to be transferred to the hospital.

There was no other way to take his sister to the morgue and her dead body was bundled in on top of his. The door on the ambulance shut and they drove off down a dusty road.

That's the last I saw of them.

Matt Brown's frontline report for Four Corners on the battle for Mosul can be seen on iView.