A Navy veteran dad was killed running into his burning home to save his 10-year-old son — not knowing the boy had already safely escaped the burning building.

Christopher Gierhart, 50, died late Sunday after a July Fourth firework appears to have started the blaze that engulfed his home in Hollywood, Maryland, Chesapeake Today reported. 

The newly engaged dad raced inside the home because he thought his son was inside, officials said.

“Initial reports indicated the child’s father had re-entered the residence in an attempt to locate the child,” Maryland State Fire Marshal said, without naming Gierhart.

“After extinguishing the fire, firefighters located the father deceased on the second floor of the home. The child was later confirmed to have safely escaped the home.”

The blaze appears to have started with a firework, the fire marshal said.

“While the fire remains under investigation, preliminary information indicates the family had been using ground-based sparkler fireworks earlier in the evening,” the marshal said.

“After the fireworks display concluded, the spent fireworks were discarded into a trash can on the home’s screened-in rear deck. 

“Deputy State Fire Marshals are investigating whether the discarded fireworks retained enough heat to ignite combustible materials inside the trash can, resulting in the fire.”

Gierhart’s cause of death is still being investigated. 

Gierhart served in the Navy for 25 years and commanded the Electronic Attack Squadron, known as the “Gray Wolves.”

He also leaves behind fiancee Lauren Copenhaver, whom he proposed to a year ago.

“What should have been a time of celebration became an unimaginable tragedy,” pal Amanda Peterson said in a fundraiser created for Copenhaver and his 10-year-old son.

“Following a devastating fireworks-related house fire, Lauren lost her beloved fiancé, Chris, their home and nearly everything they owned. In an instant, her entire world was changed forever.”

She’s now “facing the overwhelming challenge of rebuilding her life from nothing,” Peterson said.