"I work in a special unit in the millitary" kinda ruined my expectations and that would lead to a team of others like Ekuson, making the plot predictable.
That's a good point. I'm not necessarily suggesting you change that part of the plot, but maybe you should hold off on revealing it for now. I mean, it's chapter 1 and we already found out that the main character thus far is a little kid who enjoys torturing and devouring others. That's a pretty big concept. The fact that Ekuson opposes him may just be enough for us to go on for now.
Also, about adding more description to my chapter 1, what would you recommend, and where, for example?
First things first, the way I see it, there's an important question you should always keep in mind: How much do I want to leave up to the interpretation of the reader?
. . . as he wandered nonchalantly into a shady warehouse, supposedly abandoned.
Here, you describe the warehouse as shady and abandoned and then move on. Your job ends and now the job of the reader to determine what makes a warehouse seem shady and abandoned begins. Or, you could go into more detail. Tell us how this warehouse is shady. Is it the last one at the end of the docks and it never has any lights on? Are there broken windows, or as SolidShark suggested, rust and bullet holes? Alternatively, you could just give these details and not even mention that it's abandoned or shady. Let the reader determine that based on its less than ideal condition.
I don't think there's a wrong or right way to do it and chances are, there are even more ways to do it, but there is another factor that you might want consider with regards to descriptions: pacing. For example, if your character is in the middle of a fight at the warehouse, you probably wouldn't want to take the time to go into great detail about the surroundings since fights tend to be fast paced.
The bat struck the unflinching child in the forehead, but he didn't budge.
Reading this again, detail isn't the only problem I see. In this part you don't need to mention that the child is unflinching and that he doesn't budge, especially in the same sentence. They both get across the same point: he wasn't phased by getting smacked in the head with a nailed bat.
Holes were created in the child’s skin, but blood didn't come out – spikes make from shadows did, and after regressing the boy’s wounds healed.
Also keep in mind word choice. "Created" works and makes sense, but is it the best word to use in this context to create the image you want? When I hear about creation, I tend to think of something positive, not the destructive force of a bat being swung at a child's head.
Another problem I have with the word choice here is the way you describe the spikes. You refer to them almost nonchalantly whereas I think of ominous shadowy spikes seeping out of a deadly wound as horrifying.
Btw, that line is also grammatically incorrect. I think "make" should be "made" and there should be a comma after "regressing."
The teenagers started to shudder in terror as the boy's shadow extended and began to strangle the middle school children, who until now stood apathetic to the lynching that should have occurred to the boy, but was instead being carried out against the teenagers. The middle school children fainted from the suffocation but were soon awakened by the pain of having their tendon’s cut by the shadows, which were sharp like surgical steel.
Another thing I didn't pick up on last time is his paragraph. The first sentence is really long, and I'm not sure if it's even a correct sentence. I'd break it down into a sentence about the shadow and another one about the children and how essentially, the tables have been turned on them. The second sentence has the same problem as before, I think. Something horrifying is happening and you kind of just sweep over it.
The leader was thrown onto his back, and as soon as he could move, he back away with eyes wide open, crying in sheer fear of what would come next.
You could do a bit more to describe the way the leader is moving. If he just had the tendons in his legs cut, I imagine he'd have a pretty tough time.
Anyway, there's some examples. It's late and I'm tired. One more thing though. I don't know now long you've been writing or how much practice you've had up until now, but don't spend too long on the first chapter. Do not try to revise it over and over again until it's perfect, especially if this is the first story you're working on. I can speak from personal experience. It didn't work out.