Since leaving Konoha, Naruto had nearly died if not for the kind merchant family he hitched a ride with. Not only did they took him in, they even taught him how to fish for food and cook it afterward. Since they were merchants, they needed goods for trade thus they never know how to hunt and cut off the furs which they sell later. They showed him many things and treated him like a real family. For once our hero is truly happy and feeling truly normal as one should feel in a happy family.
Unfortunately, all good things lead to an end. They had the misfortune of meeting bandits. One thing leads to another it ended up killing everyone. Not wanting to have any loose ends they even killed the small girl in front of him.
This act of cruelty sent our blond Jinchuriki completely off the edge as he felt the rage he never before experienced. It felt like anger in a fluid form as it bleeds from his body and slowly coming out to the surface. He was not far off because as the red energy appears, it starts burning his skin as well as alerting all the bandits. Since then everything just turns slow motion as he completely lost himself to the rage and starts picking off everything that moves.
As for the bandits themselves, they had never seen anything like it and the first thing comes to mind was the boy is a demon. Whether Naruto hear it or not it hadn't matter as he continues to tear everything into pieces. The bandits didn't even put up a fight as they were either too scared or trying to run from the scene. They were quickly picked off as Naruto dash after them and claw through their hearts. His demonic chakra had burned everything it touches turning all to ash, including the bandits.
Sadly for our hero, he may not have control over what he had done but he remembered every detail of what he had done. He may not know why nor how it happened, but he wondered if this was the reason why the villagers called him a demon? Seeing the result of the aftermath, Naruto only felt sadness and a sense of emptiness. He did not think that what had done was bad, but what had he accomplished in the end? The people he had avenged would be happy to see what he had done? While he may believe these bandits deserve it but in his heart, he strongly believes the family he had known would be just like the villagers. Naruto had to stop himself thinking anymore because he wanted to believe they are different from those horrible Konoha villagers.
Remembering, for a short time in his life, he was happy. It was unfortunate that it was short-lived like a dream as he was once again back with nothing. He had heard of what do to the dead, so he spent some time digging their graves and dragging the bodies to them. Normally there would be three separate graves, but he felt they would be happy to be together as a family.
As for the bandits, there isn't much needed for them as the bodies turn to ash as soon as he touches them. Whatever he had done, there isn't anything left of them as the wind carried the ashes away like he didn't have to worry about them anymore. What was left were only his family and himself.
Although he was not in control of his action, to think that he could have done the same thing to others makes him feel weak and helpless. Naruto never wanted to feel like that again, so he finishes burying the big massive grave of three, he vows both not to lose control nor use that foul energy ever again. Remembering the sight as he picked up the body of the small child and how she was still alive hours ago. He didn't want to have this feeling again, in a way he felt responsible for their deaths. Swearing on their grave he will get stronger so he can protect what he holds dear to him and the same thing never happens again.
Praying for them and thanking them for their care even if it was the very sort he felt for a short time he had a real family he never had. With no friends, no family, or anyone to turn to Naruto realize he didn't know what to do.