How did senator Joseph McCarthy investigate domestic comunism

Ok, there is a lot for McCarthy. Since he was a Senator, form the late 1940's to the mid 1950's he went on a hunt for communists in the gov and in public life. He mostly did this because he wanted to ensure his political success. So during this time was the "Red Scare" aka when Americans were afraid of communism, so when he claimed he had a list of 205 communists the public went crazy and supported his crusade.