Movies and TV give us false impressions, most of the time, when it comes to firearms. While in the movies, they go "bang", note how often characters shoot inside buildings (or small rooms) and then continue to speak in normal voices, and be able to hear small sounds normally.
This is ABSOLUTELY NOT THE CASE when firing real rifles inside enclosed spaces. Without hearing protection, the shooter (and anyone else in the room) will suffer hearing damage, ranging from ringing in the ears all the way up to a ruptured eardrum, depending on the gun, and the specifics of where they are in relation to the muzzle. Hollywood NEVER shows this.
The flash is equivalent to a good size old fashioned camera flashbulb, depending on the specifics of cartridge and barrel length. For instance a 24" barrel rifle has a much smaller flash signature than an 18" barrel carbine.
A shot (even a very loud one from a rifle) inside a closed room across a four lane highway? With no traffic noise, it could be heard, if one was listening, but it wouldn't sound like a shot, more like a thump, or a pop. People (non shooters) who have been in other rooms in buildings with shooting going on often don't realize what they are hearing are gunshots. Firecrackers, or "like a lightbulb being dropped" is what they often say. And that is because the sound of the shots is outside their experience, so they pick something close that they know to describe what they heard.
Go to an indoor pistol range, and listen to what you hear outside the building. Pops and thumps. Fairly loud, close up, much less noticable further away. And (most) pistols are not nearly as loud (to the ear) as rifles.
As to the gut shot with a deer rifle, instant death is possible, but not likely. Instant unconciousness, followed by death a few minutes later from internal/external bleeding, much more likely. In your across the desk situation, a deer rifle is virtually guaranteed to go in one side, and out the other, often with enough energy to penetrate a wall or two, and even wound kill someone in a room across the street or even further away, if hit.
And, also, if death is not instant, the heart will keep beating for a bit, keeping pressure in the system, literally pumping blood out the wounds, until death. So there could be a lot of blood. But if the heart is stopped right away, much less blood, as it will only ooze out.
Lots of little things to consider, if you want to describe it realistically.
Also, while certain types and calibers are much more common in certain areas, any kind can be found in any place. Your swamp rat hunter might use a lever action .30-30 or pump shotgun for the swamps, but if he hunts down a pole line, or across a bean field, he might use a bolt action with a scope.
good luck!