(CNN) -- Michael Slager, the former South Carolina police officer who fatally shot a man in the back, intends to plead guilty to one federal charge of excessive use of force as part of a plea agreement, a source with direct knowledge of the plea deal said.
The charge is a felony and is punishable by up to life in prison. Slager is expected to plead guilty Tuesday at 2:30 p.m. ET.
Slager's state murder trial ended in a mistrial in December after a jury failed to reach a verdict. The remaining state murder charges will be dismissed as part of this plea agreement, the source said.
Slager shot Walter Scott, an unarmed black man, as Scott was running away from him following a traffic stop in April 2015.
The killing sparked renewed "Black Lives Matter" protests after Scott became the latest in a series of unarmed black men killed by police.
The shooting ... and the explanation
Slager was an officer for the North Charleston Police Department when he pulled Scott over for a broken tail light. A few moments later, Scott ran away.
A foot chase ensued, and a bystander's cell phone video captured Slager firing eight times -- striking Scott several times in the back.
Slager later said he feared for his life because Scott had grabbed his Taser. But the officer's account did little to calm the backlash over the killing.
The North Charleston police chief fired Slager, saying he was "sickened" by what he saw. And a state prosecutor filed a murder charge against Slager.
But in December, a judge declared a mistrial in Slager's state murder trial after the jury failed to reach a verdict following 22 hours of deliberations.
After the mistrial, Scott's family members said justice will eventually prevail.
"In my heart, I will find the peace to forgive Michael Slager," brother Anthony Scott said. "But at this present time, until my family can see justice, no, there's no forgiveness."