Before he was 20, August helped organize the North Berkeley Volunteer Fire Department, and in 1897, was awarded the Berkeley Fireman medal. He supported his mother and the rest of his family as a partner in Patterson and Vollmer, a hay, grain, wood and coal supply store, at the corner of Shattuck Avenue and Vine Street near a fire station north of downtown Berkeley.
In 1898, August enlisted in the United States Marines, fighting in 25 battles in the Spanish-American War in the Philippines. Vollmer left the military in August 1899 and returned to Berkeley. In March 1900, he began working for the local post office.
In 1907, Vollmer was re-elected town marshal. He was also elected president of the California Association of Police Chiefs, even though, by title, he was not yet a police chief himself. In 1909, Berkeley created the office of police chief, and Vollmer became the first to hold that office.
Drawing on his military experience, and his own research, Vollmer reorganized the Berkeley police force. Vollmer had discovered that very little literature existed in the United States on the subject of police work, so he located and read a number of European works on the subject, in particular, Criminal Psychology, by Hans Gross, an Austrian criminologist, and Memoirs of Vidocq, by Eugene Francois Vidocq, head of the detective division of the French police in Paris. He then set out on a program of modernization. He established a bicycle patrol and created the first centralized police records system, designed to streamline and organize criminal investigations. He established a call box network. And he trained his deputies in marksmenship.
In the ensuing years, Vollmer's reputation as the "father of modern law enforcement" grew. He was the first chief to require that police officers attain college degrees, and persuaded the University of California to teach criminal justice. In 1916, UC-Berkeley established a criminal justice program, headed by Vollmer. At Berkeley, he taught O.W. Wilson, who went on to become a professor and continued efforts to professionalize policing. This is often seen as the start of criminal justice as an academic field.
Vollmer was also the first police chief to create a motorized force, placing officers on motorcycles, and in cars so that they could patrol a broader area with greater efficiency. Radios were included in patrol cars. He was also the first to use the lie detector, developed at the University of California, in police work. Vollmer supported programs to assist disadvantaged children, and was often criticized for his leniency towards petty offenders such as drunks and loiterers. He also encouraged the training and employment of female and African American police officers.
Vollmer left the Berkeley Police Department for a brief stint as police chief of the Los Angeles Police Department from 1923-24, but returned upon being disillusioned by the extent of corruption and hostility towards leadership coming from outside the department.
Vollmer married Millicent Gardner in 1924. They had no children.
He retired from the Berkeley Police in 1932 as his eyesight began to fail.
Vollmer became afflicted with Parkinson's Disease late in life, and also cancer. He refused to be bed-ridden, and chose to end his own life at age 79 in 1955.