A civil complaint was filed against me

I was involved in a three-car crash on March, 2007. Basically, the first driver lost control and was hit by the second car, and my car, the third one, hit them both. The police officer said that the first driver should take a major responsibility. Today, I was surprised to receive a letter from a district court that the second driver has filed a civil complaint against me and the first driver and our insurance companies, saying that “the defendants have admitted responsibilities, but the defendant’s insurance company have refused to pay plaintiff's property damaged”. I was stunned because I never admitted any responsibility. I am seeking help from 單身老貓 or other experts. What should I do now? Contact my insurance company first or find a lawyer to defend? Any suggestion is highly appreciated. One more question, naïve maybe, I am planning to file I485 next month, will this case affect my green card application? Thanks again.