"Procedural due process is a legal doctrine in the United States that requires government officials to follow fair procedures before depriving a person of life, liberty, or property. When the government seeks to deprive a person of one of those interests, procedural due process minimally requires for the government to afford the person notice, an opportunity to be heard, and a decision made by a neutral decisionmaker. Procedural due process is required by the Due Process Clauses of the Fifth and Fourteenth Amendments to the United States Constitution."
They deprived him of his life and did not afford him notice, the opportunity to be heard, or a decision made by a neutral decisionmaker.
That's why people are skeptical when Holder said his death met the requirements for due process.