I was there.
I was there when a man ripped through five steel doors and tore men in half with his bare hands. I was there when horrible things erupted from a plane in mid-flight and set the sane world ablaze. I was there when the green made the dead dance and scream.
I was there when the orders came through, when those orders were carried out, and when they told us they needed to be carried out once a day, every day, for the rest of her life.
I was there when the two best men I have ever known crumpled in an instant because they looked away, and I stood there, staring into that ridiculous face…
That absurd, ridiculous face.
That was the last time anything ever surprised me.
When I woke up in an infirmary bed to be told that I had been promoted, I wasn't surprised. When they told me that they had falsified my death and administered amnestics to the people who knew better, I wasn't surprised. When they brought me to Command and I met the others, I wasn't surprised. Then they told me that, as part of the O5 Orientation, they were going to explain to me what SCP-001 was…
I wasn't surprised.
When I met the rest of the council, they told me that as per protocol, I would be given an introductory letter from the Administrator. When I asked them where the Administrator was, they simply told me "We don't know." I almost laughed; didn't the O5 know everything? They handed the letter to me and left the room, when I asked why they were leaving, they said, "For privacy". I merely blinked at him; at this point I wondered whether the whole thing was a joke. So I sat down in the chair they left for me and opened the piece of paper.

Welcome, newly-appointed overseer.
You have questions. Perhaps you don't even know what they all are, or care what the answers are at this point, but you have them, and you have many. If you opened this letter expecting those answers, I will tell you all that I have.
Which is none.
What is SCP-001? There isn't one. Was there a first anomalous object that was discovered? Of course. Was it important? Probably not. Confused? Good. At least you're still human. That's all we are, human beings. Human beings that thought we could reliably record the destruction of sanity. We were fools. We still are. The Foundation is compromised, it always has been, and it always will be. Why? We thought that there was a linchpin, a reason for it all—it's because we thought there was a "why".
There wasn't one.
This is the way things are. Nothing has changed, the universe hasn't broken down over time, this is how it's supposed to be. Personnel are told about SCP-001 because it comforts them. It helps to think there is a why, because that suggests that there is a solution, but there isn't. We do not repair: we secure, contain, protect. Surely you must have wondered why the objects are not numbered chronologically, in order of recovery? Surely you must have wondered why some objects have fully documented histories and others don't? Surely you must have wondered, given everything you know, why this world even still exists? See, I told you that you had more questions than you thought.
We don't know how much of what we documented is true anymore, it probably changes from day to day. There's no way of telling what is being affected by what anomaly, especially when there could be an infinite number that we haven't even discovered. Existence is an anomaly.
So what do we expect you to do, armed with this information, or lack thereof? Whatever you can. We do not repair, and we do not solve.
We Secure.
We Contain.
We Protect.

Congratulations on your promotion to overseer.
Good luck.
-The Administrator

I was there when not caring was not good enough to protect me from the truth.
I must have sat for an hour before they came back for me. When they asked how I was, all I said was: "A little surprised." They looked at me and I heard the voice, faintly, "Welcome to Overwatch, Brian." The rest is history, if such a thing exists. There is one more thing, though, the letter had a PS:

Don't worry about it too much, whatever you think is the truth is probably good enough anyway.