Major David Ellwood began his law enforcement career in his hometown with the Baltimore City Police Department in 1990, serving as a Patrol Officer, Narcotics Detective, and Violent Crimes Detective. He is a fifth-generation police officer as law enforcement dates back to the late 1800s in his family.

In 1997, Major Ellwood moved to Florida. He joined the Broward Sheriff's Office as a deputy sheriff assigned to the Deerfield Beach district. He has served in various capacities since then as he has risen through the ranks of BSO. In December 2018, he was selected as the executive officer of the Fort Lauderdale/Hollywood International Airport District. He was promoted to Fort Lauderdale/Hollywood International Airport district chief on October 12, 2019. He was promoted to major in March 2024. 

Major Ellwood holds a Bachelor of Science in Criminal Justice Management from Union Institute and University. He has received numerous awards, honors and commendations over his 30-year law enforcement career. He is an active member of the Broward County Chiefs of Police Association (BCCPA) and the Airport Law Enforcement Agencies Network (ALEAN). Major Ellwood is a graduate of the University of Louisville's Southern Police Institute, 88th Command Officers Development Course.