Unknown router connected to my password protected network

I just got my self installation kit set up last night, and when I woke this morning the first thing I see is a router connected to my gateway at around 3 AM. Its not my router and has no IP address showing. Ive changed my wifi password from the default during setup. I keep trying to turn on the security option in the xfi app and it tells me theres a problem and to try again later. This is incredibly frustrating