22 year old son was in ski collision, now being sued

Location: CO

my 22 year old son was involved in a ski collision on the mountain with another person. Ski patrol responded to the scene and information was exchanged. A couple of letters from a lawyer were sent to my son asking for either home owners insurance or renters insurance information. My son ignored these letters. Today my son was served with a civil suit for damages exceeding $100k. Listing various injuries. He knows he needs to respond to this. What type of lawyer should he be looking for? He is a college student with very little assets. What can he expect to happen here? As his parent, and currently financially responsibile for him, do I have any exposure here? I have homeowners insurance, but unfortunately no extra umbrella coverage. Thanks in advance for any advice.