Mr. McPherson, 50, died at about 5 p.m., according to Jim England, an employee of Thomas L. King Funeral Home in Martinez.
Mr. England said he did not know the cause of death.
Mr. McPherson, who was married with children, was taken to Doctors Hospital from his home on Wheeler Road, Mr. England said.
It wasn't clear whether he died at home or en route to the hospital, he said.
On Sunday night, Martinez-Columbia Fire Rescue Chief Doug Cooper said he and others who worked in his department were "in shock" over Mr. McPherson's sudden and unexpected death.
"He was a beloved member of our department," Chief Cooper said. "Tommy had been a firefighter for many years - starting as a volunteer while still in high school. He recently rejoined our department as a full-time firefighter, stationed at Engine Company 16.
"He'll be greatly missed by every member of the fire department. Our thoughts and prayers go out to his family," he said.
Reach Timothy Cox at (706) 823-3217 or firstname.lastname@example.org.