Jason Eagan, a volunteer firefighter in Sandoval, Illinois, reportedly left the department after suffering at the hands of several bullies within the department.
She wrote, "My brother, Jason Eagan, has Down syndrome and became a fire fighter in Sandoval, IL.
"It disappoints and angers me that this was allowed and that a grown man bullied a fellow fireman simply because he's different," she added.
Eagan returned to his job on Monday after a three-month break, and the Sandoval Fire Department is set to hold a meeting about the incident later this week.
"It went good for two [or] three years and then, all of the sudden, someone at the fire department started harassing Jason and picking on him and bullying him," Eagan-Robbins said.