Default [Q] Galaxy S5 just rebooted with an unlocked lock saying "custom" powered by android

Ok, so I was just chilling with my new S5 and all of a sudden this thing rebooted. I didn't think much about it, but the thing is that when it rebooted insted of the bootup saying "samsung galaxy S5 Powered by Android" it said "Samsung Galaxy S5 (unlocked lock icon) custom Powered by Android".

Now I rebooted it again and the same thing happened. Now I did not root my phone or unlock or anything. All I did was enable developer mode because I like the show touches option and switch over to ART from Dalvik.

This is the SM-G900A.

ADDENDUM: I just got this phone four days ago. Switched from JB iPhone 4S