Why did my phone shut down,

[Android Central Question]

I was using my emails and all over sudden my phone shutdown i tried to open the screen lock with the 4digit of which it displayed that i put a private security password of which i couldn't remember..
How can i retrieve the of Private password...
Kindly help

 

[belodion]

You'll probably have to factory reset, which of course will wipe all personal data not already backed up.

Why it shut down I don't know.