network switch issue when attempting to connect phone to pc

Heres the structure: internet to switch, one cable to pc from switch, one cable to phone from switch (we have internet based phones). This provides both with internet access. I then took a cable and put it into the pc connection jack on the phone and plugged it into the switch attempting to connect the phone to the pc (trying to integrate the phone system with our CRM). This caused a loss of connection for the phone, the local network for the computer and internet to fail. I then had a coworker come to me and say they just lost internet as well. What the heck happened?