El Fasher had been a sanctuary for many who had fled their homes because of the conflict. But it has now turned into yet another frontline.
Civilians there have reported being hit by shelling and bullets in their homes and even in hospital.
One of the last health facilities still running is the Sayyid Shuada health centre.
Footage filmed in the hospital for the BBC shows a distraught mother too shocked to speak after shelling hit her home, injuring five family members.
She held her toddler as her husband and other children received emergency treatment.
The mother said she couldn’t tell whether the blood on her toddler’s face was his, his siblings’ or his father’s.
Sayyid Shuada is overstretched by the mounting casualties.
“Every day there is a new wave of patients that are wounded arriving… on average maybe 50 per day, which is already what we consider mass casualty,” said Claire Nicolet, who leads medical charity MSF’s emergency response in Sudan.
There’s only one surgeon present at the facility who is forced by the situation to work “round the clock”.
“Most of [the patients] need surgery so it’s pretty dramatic,” says Ms Nicolet.
Local community volunteers have formed committees to try and support the hospital. They take care of non-medical tasks, like finding water and fuel and collecting data.
Volunteer Khalid Abdul Hamid tells the BBC that committees are collecting donations of cash, goods, and services from the already war-battered community.
“From our own efforts and the efforts of well-wishers, we have managed to get some medicine… or cash contributions to buy medicine from the local market,” he said.
The situation is deteriorating by the day and an increasing number of facilities are put out of operation by the fighting.
On Saturday, RSF fighters stormed the South Hospital, a referral hospital that was treating civilians wounded in the war. Gunmen opened fire and looted the facility, stealing an ambulance.
The hospital, which was also ran by the medical charity MSF, has now been closed.
Its head of emergencies, Michel Lacharite, said the attack was outrageous. “Opening fire inside a hospital crosses a line,” he said.
The South hospital had been hit by shelling and bullets at least three times in 10 days before the Saturday raid.
A pediatric hospital managed by the MSF in El Fasher was bombed in May, killing two children.
The constant shelling in El Fasher has sent tens of thousands fleeing once again. Most are heading towards Sudan’s west, with options for safer places running out.
“We need this to end,” Mr Perriello said.
“We need cooler heads to prevail and get this particular battle paused, while also we don’t take our eye off of other parts of Sudan.”