You should say "There are some people" (not "is"). In nearly all contexts, people is a plural noun. One person, many people. Here, "people" means many individual human beings. There is another specialized use where "a people" means a tribe, a nation. You might talk about, for instance, "The peoples of the Mediterranean lands". This is much less common, and somewhat formal sounding. Note: in some situations, especially official statements by government officials, you might see "persons" being used as the plural of "person", instead of "people". For instance, the police usually talk about "missing persons". But in everyday use, "people" is just the plural of "person".