According to the Galveston Fire Department, crew responded to a call of a structure fire around 8:45 p.m. in the 4300 block of Avenue Q 1/2.
Two people were inside at the time of the fire.
The fire department said a man, who was identified as 79-year-old Benjamin Laughlin, died at the scene, while a woman, 76-year-old Lillian Laughlin, was transported to UTMB in critical condition.
On Thursday, fire officials said Laughlin succumbed to her injuries. The couple's canine also died in the fire.
The cause of the fire is under investigation.