He was then assigned to the HHC 130th Engineer Battalion at Vega Baja, Puerto Rico where he served as Utilities Maintenance Technician.

[5] He served in this position until 1985, all the while in 1982, he was promoted to the rank of major and in 1983, he attended the United States Army Command and General Staff College in Fort Leavenworth, Kansas.

From 1985 to 1990, Díaz-Colón was given a Federal position when he was placed in charge of the Housing Urban Development (HUD) in the Caribbean.

As adjutant general, he was the governor's senior military adviser and oversaw both state and federal missions of the Puerto Rico National Guard.

He also provided effective leadership and management in the implementation of all programs and policies affecting more than 11,100 Puerto Rico National Guard citizens-soldiers.

He thus became the first person who was a former adjutant general of the Puerto Rico National Guard to be named to that position.

[2][6] Díaz Colón entered the Police Department in the middle of a record-breaking year in murders in Puerto Rico, and has received harsh criticisms ever since from various sectors.