Hello, My 13 Year Old Son Started Having What He

Hello,
My 13 year old son started having what he described as a "gassy" feeling stomach tonight before football practice. He was able to do practice, then came home and had dinner. About an hour ago he said his stomach felt "gassy" again and went to use the restroom. He had a small BM but with in minutes was vomiting. He has been in the bathroom vomiting for the last hour. When I went in to check on him, I also noticed a red rash on his mid-thigh that is about 3 inches in diameter. He said he noticed it this afternoon, but forgot to mention it to me. I am wondering if this sounds viral or like something I should have checked. Thank you for you help.