How did senator Joseph McCarthy investigate domestic cominism

He targeted and attacked various people.

Senator Joseph McCarthy used his position as a Senator to commence and rile up hearings to see if America had been infiltrated by communists.

His basic tactic was to throw a wild net and accuse a wide range of government officials and well known Americans of being communists and then bring them in to testify under oath. He would urge them to name names of people that they knew to be communists to let them go free.

Eventually, McCarthy's accusations went too far and people started to firmly push back.