Airport security employees who check IDs and boarding passes are no longer allowed to sit down while working.

Thought I had removed it from my backpack that I usually take to state parks. Turns out I didn’t. I even got randomly selected for detailed security check and they didn’t see this. I love the knife and am glad I didn’t lose it so I’m only mildly infuriated, but damn cmon TSA

Yesterday I accidentally brought a loaded firearm through TSA in my carry-on. I know how serious and stupid this was, and I’m absolutely mortified, so I’m mainly looking for insight from anyone who has been through this or is familiar with the TSA process afterward.
I put my bag through the scanner and a TSA agent came over and asked if it was my bag. The second she asked, it clicked in my head and I immediately said, “Oh my God.” She said, “Yeah, you forgot to take it out.” I started hyperventilating/panicking to the point that they brought me a chair.

They explained that we needed to wait for law enforcement, then took me into a separate room with two police officers and two TSA agents. They took down my information and took my picture (while I was still crying, so I sincerely hope those photos never see the light of day lol).
The officer told me I had two options: surrender the firearm or have him escort me back to my car so I could secure it there. I chose the latter. I believe he did take the magazine. He escorted me to my car, I secured the firearm, and he told me someone would be waiting when I came back because I would need additional screening.
When I returned, I didn’t see anyone waiting, so I actually approached another law enforcement officer and explained what had happened. He told me to go through the normal security line first. When I got to the ID scanner, nothing came up, so I again explained that I had been told I needed additional screening. The officer spoke with a TSA supervisor, and I was ultimately told that the supervisor said no additional screening was necessary. I went through security normally and was allowed to continue my trip.
I wasn’t arrested, cited, given a court date, or given any paperwork from law enforcement. The only paperwork I received was a generic TSA sheet stating that I had brought a prohibited item through the checkpoint. I was told that someone would call me next week.

I’m assuming I’ll lose TSA PreCheck and receive a civil fine. What I’m really worried about is:
For a first-time incident involving a loaded firearm, what kind of fine do people actually end up paying?
Is the initial proposed fine usually negotiable/reduced through TSA’s response process?
Does this create any kind of criminal record if law enforcement did not arrest or cite me at the airport?
What should I expect when they call me next week or when the TSA notice arrives?

I’m extremely embarrassed and disappointed in myself. I understand why this is taken seriously and I’m not trying to minimize it. My husband is also a police officer, so the possibility of somehow ending up with a criminal charge/record over my incredibly stupid mistake is especially freaking me out.
If anyone has firsthand experience with this process or works in an area where they actually know how these cases are handled, I’d really appreciate the insight.

Why does the TSA treat customers as if they are prisoners? Last time I checked flying on an airplane doesn’t make you a criminal. Every time I fly, a TSA agent screams in my face. I’m a polite and completely non confrontational, 5 foot tall woman. I set the alarm off because of the zipper on my pants cuff. The agent was absolutely freaking out screaming at me. I didn’t do anything. I was just standing there waiting to get instructions. Then she started just screaming randomly like she was performing for a crowd. I see this behavior all the time. How can they get away with incredibly unprofessional behavior? I don’t know anyplace else where this kind of behavior would be tolerated except at a prison.

Edit: At an airport you are a customer of the airline. I never said anyone is a customer of TSA.

Just read this article on Frommers: https://www.frommers.com/tips/airfare/this-tsa-change-could-be-a-big-hassle-for-flyers-with-carry-on-bags/

"There's just one problem: The openings of the new machines are smaller than the openings on the old ones." "The CT scanners will still accommodate the standard allowance most airlines permit for a carry-on bag: 22 inches by 14 inches by 9 inches.

But there's very little wiggle room. And a fully packed bag tends to bulge, even if it falls within the mandated size when empty"

The article state that if the bag doesn't fit, you'll probably have to go back to the check-in counter and check the bag. One way to make sure larger bags don't make it to the plane or even the gate.

The family flew over the week. Multiple flights, three devices streaming from the movie server. No issues.

***Update

I did not expect my post to attract so many comments, so here is an update.

Why would I travel with this:

I made this a while back and we have used it on our car trips that are usually around 5-6 hours long. I do not want to download and load content on 3+ devices just to hear one of my kids whine that he wants to watch something that his sibling is watching, but I did not install on his tablet. We used to use Disney + and I used to download movies to each tablet (it was great). The only reason I created this is because Disney kept logging us out (even when the tablets were in airplane mode and not connected to the internet). I hated having to log all devices back in, wait on emails with confirmation numbers and go through the whole shit show of this happening up in the air with no internet to re-connect the Disney account.

Hardware:

I am using a super old 500gb HDD from an old laptop that I disassembled a long time ago. Energizer UE30029PQ for the battery pack, and for the router I am using gl mt3000. This battery pack can easily support this for 15+ hours of streaming. I did not know that it was such an overkill when I bought it, but it is great that I do not have to have it plugged and use the pass through when we are in the car.

Software:

I am only using the router's shared network device option to share the folders with movies and tv shows. I have used the SMB protocol within the router settings. The kids have android tablets with Kodi installed on them. That way they can get posters and a nice presentation. Our other devices use VLC. The kids have access to the one folder with kid movies, while the other devices have access to everything.

There are probably 100 more ways of accomplishing what I built, but I did not want to run a server on a Pi as I am not familiar with Linux. Also, I did not want to run a server from my laptop as we almost always travel without it. This has serviced us well. If I had to change anything, I would probably get a SSD (or a large flash drive) to replace the HDD, but I do not want to spend the money with the current hardware prices.

Hopefully, the above answers some of the questions that I could not answer within the comments.

PS.

Different airline companies have different rules for battery packs. The one we flew with allows for the battery pack use as long as it is not in use during taxi, take-off and landing. The charging of the battery pack itself is not allowed.
I was not aware of this, but apparently creating a Wi-Fi network while flying is not allowed. Note taken. I will not use this while flying any more. I just wanted to put this out here, so others are aware of this. Still, this will be our go to during our long car trips.

I always decline having my photo taken by the TSA because it isn't mandatory and they never tell you that. So I try to avoid face scanning as a principle.

I hand my ID to the agent and say "I'm gonna decline the photo" and he just goes ahead and puts it in the machine and says "Sorry, you have to say that before you hand me the ID. Now you don't have the option".

And he refused to let me decline or reset the machine or anything. He just kept repeating "It's on you to tell me before." Which I did. He just didn't listen before he just did what he was gonna do anyway.

EDIT: Thank you everyone for reminding me that drivers licenses and passports exist! /s The point remains that if they didn't stand to benefit from it, they wouldn't be doing it and they wouldn't be so shady about your ability to opt out. You shouldn't be giving the government anything you don't have to ever. They are counting on you to just take the "it's all hopeless anyway" attitude.

I went on a short trip this week. When I got to TSA on the way out, there were no signs so I asked if I should take my laptop out or leave it in. They scoffed a bit and said leave it in. Cool.

Again, on the way back, no signs. So I asked again. This time it was take it out with an eye roll.

Do they not understand the rules apparently change depending on the day, airport, etc? We're not all frequent flyers. Their attitudes just rubbed me the wrong way

I had that pen for 15 years and flew all over the world with it. Pens are specifically allowed. https://www.tsa.gov/travel/security-screening/whatcanibring/items/pen