ProPublica is a nonprofit newsroom that investigates abuses of power. Sign up to receive our biggest stories as soon as they’re published. Marshall Allen, a former ProPublica investigative reporter who relentlessly took on the U.S. health care system and fought for the rights of patients facing unfair medical bills, died Sunday at a hospital in the Dallas-Fort Worth area. He was 52. The cause was a heart attack, said Sonja Allen, his wife of 29 years.