I had been travelling with Erik the slayer from Rorikstead for a long time now, I game him an awesome battleaxe that drains health
and I gave him a full set of daedric ebony armour that lets him sneak better.

After travelling for so long together, we went into a cave full of drougr and witches, I wanted to test some undead scrolls given to my by jzargo in the college of winterhold. The scroll engulfs you in flames and what not. During a fight, I accidently hurt Erik with the fire, he got mad, drew his axe and started attacking me. I sheathed my weapon to calm him down, and he stopped fighting me.

After everything went back to normal, he started attacking me again, I kept putting my weapon away to calm him down, but he didn't stop.
I ran out of the cave, waited a while, then came back in. I walked slowly to the end of the cave, and I heard: "Is somebody there?".

This was Erik...he had become an enemy.
He had removed all the armour I gave to him, stripping all his allegiance to me, He then attacked me, So I fought and killed him.

I am going to leave 2000 Gold to his father in Rorikstead, as a token of my gratitude.

What on the earth happened here?

He thinks you're about to dump him for J'Zargo and he's really really pissed.

You obviously hurt his pride as a warrior....

The fire around you will of kept damaging him so putting your weopan away will not help when YOU are the weopan

Did you manage to recover all the things of value you gave him?

ruairi...he attacked me when the scroll was stopped.

and yes, I got all my valuables back haha.

Faendal once attacked me 2 steps from Whiterun and would not yield so i ran since i did not want to kill him...he never forgave me and i even had a bounty added to whiterun for no crime