Study industry standards and formatting. You'll learn a few options to help you convey what you want on screen.
INT. WAREHOUSE-DAY
A ruptured building comes into view. The camera pans up to reveal demonic scramblings throughout the building.
Don't waste valuable space by repeating information given in the heading. A warehouse is a building. Pointing that out in the narrative description is unnecessary.
Also, "A ruptured building comes into view" sounds like an EXT description and had me rereading the heading. Be careful and clear, because a lot can go wrong in the steps it takes to go from your mind to what a reader visualizes.
"Comes into view" doesn't tell me anything about the building. What you write is what'll come into view and what we'll see. On the other hand, ruptured does double duty by giving me an image and a mood.

We then glide into a room, revealing a corpse and a man lying down, revealed to be shot in the leg. His name is EDWARD (mid-20s). He lies panting and sobbing at his condition.
"We then glide into a room"
-A new heading is required with each change in location, even if you are moving within one structure/building.
-Noting an event or action took place next (then) is unnecessary, because they should be written in the order they occur. Otherwise, you're either pointing out the obvious or have them in the wrong order--which would make for a bumpy read of going back and forth to sort things out.
-Glide into a room? Unnecessary direction I couldn't see, especially since it's We doing it.
"...revealing a corpse and a man lying down, revealed to be shot in the leg."
-Revealing and revealed reads like 'We see' and 'We hear.' What is revealed is what you write. It's one thing if a character is revealing something to another, but when the screenwriter is revealing something to the one reading their script, it's unnecessary to write it's a reveal. Describe what's revealed, not that you're revealing something.
Someone walks into the room and stares at him; not revealing the face. Edward being wheezing.
He backs into a wall as the killer walks toward him.
Someone tugs Doe to turn him around. Revealing Edward from earlier.
In the first quote, Someone is used for the killer. In the second, Someone is used for Edward. You can't be so lax with how you refer to characters. Be consistent with character names.
There are ways to keep the killer's identity from the reader without confusing them later in the script. Read scripts and read up on industry standards to learn those ways.
A man's body is crucified to a tree.
No matter how small the part, and whether you want to keep their true identity a secret, ALL CAPS a character's name--or whatever designation you're using (such as SOMEONE)--the first time.
Out steps the main character JOHN DOE (mid-30s).
You shouldn't have to point out that a character is the MC. Providing insight into their personality when introducing them let's us know that character isn't a random jogger we'll never see again. We should also be able to tell who the MC is by their actions (just like movie goers).
Revealing Edward from earlier.
Edward is in a building with a gunshot wound to his leg when we meet him, then he's with Doe at a crime scene. Is the opening scene a flashback? If it is, look into how those are written. If it isn't, clarity is needed. If all but the first few scenes are a flashback, you can use superimpose and a reference of time (1 week ago) for one long flashback. Read Saving Private Ryan for an example. I believe SUPER is used in a similar fashion in that script.
If you don't want the reader or audience to know it's Edward until Doe turns, rewrite the scene to show this, instead of telling us it's revealed.
Doe walks towards the crime scenes to see a horrific, brutal murder.
A man's body is crucified to a tree. There are words scribbled onto a tree.
Walks- This term is used so much it stands out. There are a lot of options to give us insight into a character or the mood.
Are you left with the same impression when a character marches, sashays, slogs, strolls, or roams? I'm not either. That's why I thought "Doe stares at Edward for a while, who walks away." was an opportunity lost.
Horrific, brutal murder could mean anything from an ice pick in a pincushion of a corpse to a bloody swath of land leading to a bloodier wood chipper. I can only see what I imagine is horrific and brutal. When I get to what you want me to see, I have to replace my image with yours. Don't be vague. Be clear from the start.
Doe stares at Edward for a while, who walks away.
Order of events clarity- Does Doe stare and eventually Edward walks away? Or does Doe stare as Edward walks away? As written, the first image is Doe staring, so Doe staring at Edward is how it unfolded in my mind. Eventually, I guess Edward tires of Doe's staring, because Edward walks away.
My gut tells me Doe stared as Edward walked. If that's so, your reader has to rearrange the events they originally imagined. That makes for a clumsy and frustrating read.