Strange finding on my AWS Server

This morning when I logged into my workstation, I found that one of my putty sessions to my AWS server had gone "inactive", I looked at the content of what was on the screen and I saw:

Broadcast message from root@ip-10-166-###-###
        (unknown) at 10:08 ...

The system is going down for reboot NOW!
Control-Alt-Delete pressed

So this raises several questions in my mind:

• The Amazon AWS EC2 systems have real virtual consoles that are interactive?
• Who has access to these consoles?
• How and why would someone press "control-alt-delete" on my console?
• etc...

This also caused a problem for this website when it came back online due to a permissions issue, the content was here, but the stylesheets weren't loading so the site looked like garbage for nearly 7 hours.

Luckily, none of the other sites had this problem.

Needless to say, I will be making some changes in my AWS instance today, but does anybody have any advice they can offer?