Man stood over 66-year-old great-grandma as she bled out after he stabbed her 18 to 20 times on commuter train in unprovoked attack: Cops

Inset: John Elijah Matthews (Fulton County Jail). Background: Police investigate after Matthews allegedly stabbed a 66-year-old woman to death on a MARTA train in Atlanta (WXIA).

A Georgia man allegedly stabbed a 66-year-old great-grandma 18 to 20 times unprovoked on a commuter train and then stood over her and watched her bleed out.

John Elijah Matthews, 25, is charged with murder for the stabbing death of Margaret Swan on a MARTA train in Atlanta. Warrants obtained by local NBC affiliate WXIA say the incident occurred shortly before 11:30 a.m. Saturday near the Oakland City MARTA station.

Swan was reportedly sitting alone on the train when Matthews entered and stood near her. He allegedly took out a pocketknife, opened it and cut her in the throat. The victim tried to get away, but Matthews reportedly continued stabbing her before he threw her to the ground. He allegedly stood over her until the train arrived at the station less than two minutes later.

Officers rushed to the scene and spotted Matthews getting off the train, knife allegedly still in hand. He was arrested. Cops tried unsuccessfully to save Swan's life.

The warrants reportedly noted that Matthews and Swan never interacted with each other and the attack appeared to be unprovoked. Matthews refused to speak with detectives when they questioned him.

On Tuesday, federal authorities charged Matthews with committing an act of violence causing death on a mass transportation system.

"Margaret Swan was an innocent woman simply trying to get to her destination. My hope is these charges will bring justice for her and her family," Marlo Graham, special agent in charge of FBI Atlanta, said in a statement. "This crime also impacts everyone who relies on mass transportation to move about their daily lives. Using Atlanta's train system should be safe and free of violence."

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Swan leaves behind three children, five grandchildren and four great-grandchildren, according to her family.

"Her life was stolen for no reason," her daughter, Shanae Sams, told local ABC affiliate WSB. "My mom was on her way home from leaving from my sister's house."

Sams called her mother a "phenomenal person."

"My mom was the rock of the family," she told the TV station.