Troy Phillips was repairing a propane filling station on Cape Cod one afternoon last October when his mother called, her voice frantic.

“Something happened to Scott!”

Phillips’ younger brother Scott had been rushed to the hospital. Troy’s first thought was that Scott, who worked as a truck driver, must have been hurt in an accident. His mother was so upset on the phone that he could barely understand what she was saying.

Then she blurted out, “He died!”

At Rhode Island Hospital, Phillips learned that his 46-year-old brother had stopped for lunch at a Subway sandwich shop, in Cranston, when he collapsed.

The cause of death was hypertensive cardiovascular disease, according to his death certificate.

In the months since his brother’s death, Phillips — a volunteer firefighter and licensed EMT — has been trying to piece together what happened the day Scott died.

“Being an EMT,” Troy Phillips said, “you just want to know, what happened?”

But he keeps hitting a wall.