Solved Police At Our Door for Mysterious Hung Up 911 Call

About 30 minutes ago, the police came to our door and said they had a 911 call come from our house that was dialed and then hung up before they answered. No one in the household used any of the landline phones today... I looked at one of the phones and it said "Line in use". When I picked up a phone and put it to my ear, I heard weird static and a faint beeping noise in the background. This beeping usually happens when someone hangs up on you and you forget to end the call, so I tried to end the call by pressing the "OFF" button, but the phone's screen still said "Line in use" and did the same thing when I picked it up. They said they tried to call back after the hang-up and the line that was off the hook probably gave them a line busy tone. So they left and I unplugged the base unit from the telephone line, and I still think it's still off the hook. How would've it dialed 911 and hung itself up?

P.S. Our phone provider is going to look at it tomorrow...

Eventually, we found out it was because of static. The way our static sounded was white noise with short clicks, and it caused the phone to be stuck off hook. The clicking noise was interpreted as rotary dialing tones by the phone box thing, and eventually the static clicked out 9 fast clicks and 2 slow single clicks, causing it to become 911 in rotary form. Thus, the police were called, and all they could hear was static. We got the static fixed though so it's all good!