Dennis J. Fagan, a retired Sayville schools teacher and major general in the U.S. Army National Guard, died peacefully on June 19, having battled against a rare form of blood cancer.

Funeral services for Fagan, 73, are Wednesday, 2-5 p.m. and 7-9 p.m., and Thursday, 2-5 p.m. and 7-9 p.m., at Mangano Funeral Home in Middle Island, located at 640 Middle Country Road.

A funeral mass will be celebrated Friday at 10 a.m. in St. Mark’s Roman Catholic Church in Shoreham, 105 Randall Road.

Fagan worked as a technology teacher at Sayville High School and in the Half Hollow Hills school district for more than three decades, while also advising the development of the school yearbooks.

After he retired from teaching, the Bronx native and SUNY Oswego graduate continued advising the yearbook staff at Sayville High School. He also supervised SUNY Oswego students who worked as student teachers at many Long Island schools.

The son of a U.S. Army brigadier general, Fagan’s second career was as a U.S. Army National Guardsman. He served in the guard for nearly 30 years, retiring with the rank of major general.

Fagan started his National Guard career as a private in a signal company in Syracuse while studying at SUNY Oswego. After graduation from the college, he transferred to the 7th Regiment Armory on Park Avenue in New York City and to the 1st Battalion 107th Infantry — a unit his father, grandfather and grand uncle had proudly served previously.

Across a distinguished military career, Fagan supported, planned and executed various combat, combat support and logistics exercises, and prepared plans and trained for civilian and state government disaster control and recovery operations.

Fagan is survived by his wife Jane; his four children and their families, Jennifer and Dave Tomforde, Timothy Nina Fagan, Keri and Michael McLaughlin and Kelly Fagan; eight grandchildren, Dylan, Jackson, Carter and Olivia Tomforde, Cali and Luke Fagan and Aiden and Ryan McLaughlin. He is also survived by his two brothers, Lt. Colonel Dudley Fagan and Dr. Kevin Fagan, and his sister Barbara Young.