Yes it is the police

It the police  seems our phone has a way to dial 911 even if phone screen is lock how do i know my phone has dialed it a few times by accidemt. So its not a prented call and if it does dial  in lock mode does does not show up in call.log

OK, problem solved.
This number is a legitimate trunk line from Fairfax County police dispatch.  So yes, the person saying they just received a 911 call from your home was legitimately a police officer following up.
You can't call the number back and speak with anyone because it's a trunk line.  However, you can call Fairfax County non-emergency police phone at 703-691-2131 and confirm that it was "really" them.  

This is actually a Police number, many of the numbers in the Massey building specifically derive from this number, the reason it doesn't allow you to call back is that when you received the call it included their extension and the phone company wont back track the extension for you.
TLDR; This is actually Fairfax County Police department, they are not pretending. Also, this does not always mean you called 911 by accident. I am currently in the process of becoming a Police Cadet so this is where I normally get phone calls from when being contacted by the hiring manager.

Got the same call but had not called 911. Called Fairfax County Police and confirmed that it was legit. They had it on the log and said that call back to that number will not go through. This was during a snow storm, so maybe the phone system got jacked to make the original 911 call to them.

I got the same call on march 3rd, 2013 to my cell phone.

Correct- this tele# was a call back in response to my 911 call. A valid Ffx Co Police No. Not rude. Not a scam. Doing their job in response to my 911 call.

I think this is the emergency center

Left a message saying "This is the fairfield police department responding to a 911 call made from this number". I haven't made a phone call from my cell phone all day.

They called me and I said there was no emergency and the lady on the phone was screaming at me to give her my name! WHAT?

It is in fact. FXCO Police Calling to verify a 911 emergency call.

A woman called saying she's from 911 pretending to be police

Just had this number call my cell number 2 times. I didn't answer because I don't answer numbers that I don't know.  When I called back, it said this was not a published working phone number.  I located that it was called from the Vienna/Fairfax area from a landline.  Weird!

Called my unpublished home number.

I recieved the same call....

Fairfax County Government Police Department (703) 877-3715 - 4890 Alliance Dr, Fairfax, VA, 22030 there are other fairfax county government numbers on 703-877 , so it is likely that this is in fact a police number.

I have a blackberry that will do an emergency call pretty easilly if I hit the wrong combination of keyswhen it is locked...

Person called stating that they were the Fairfax County Police Station responding to a 911 call from my cell phone that I did not make.

Yes. they call me last night and pretend to county police station too. Ask for name and hangup. Is anyone ever know who are these people?

They called me saying "are you alright there was an outgoing 911 call from this phone". I said it must have been an accident. They said "must have been, thanks for picking up". The guy had a bad attitude also.

Called me and said 'this is the police, we just had a 911 call from this number' I do not have any outgoing call listed to 911 on the phone, which is a cellphone. Tried to call back and hear a message saying this number is not in service.

They called me at 12;17  and it's not a working number  WTF

called me at 11:35 p.m. on MY unpublished number.  i call back and it's apparently not a working number...but they JUST CALLED!