Unable to Delete a device on my network that is NOT mine

Your installer was out here several days ago to install your modem/router Gateway. After he left I noticed a device connected to my network that is not mine. It is called "Liberty Safelert"
The only person with my Internet network password was your installer and this device is clearly not mine. I googled the device Liberty Safelert and it appears to be a wifi device used to monitor a gun safe.

I do not own a gun safe or this device. How do I delete it from my network your AI chat assistant is not helpful. The only thing I seem to be able to do is "PAUSE" this device however I want it deleted from the network.