 Execute the office of Montgomery County Chief of Police. Montgomery County Chief of Police. Mark Yamada has been sworn in as the 18th Chief of Police for the county in a ceremony attended by his wife and two of his four kids. Yamada rose up through the ranks of Montgomery County Police during the past 35 years. He has specialized in community policing. Yamada replaces retiring Police Chief Marcus Jones, who will now run security for the county school system.