David Robinson, 53, is now charged with murder and two counts of manslaughter.
Police had identified him as a suspect shortly after the July crime and he was arrested Friday afternoon.
"This was a terrible crime over the summer and our hearts continue to go out to the victim's family. Once again it is clear that with cameras in every subway station anyone who preys on transit riders can expect to be identified and face justice. We urge prosecutors to be as aggressive in court as the NYPD was in its investigation," MTA Communications Director Tim Minton said in a statement.
Police said 58-year-old Than Wtwe Than was with her 22-year-old son walking up the subway stairs at the Canal Street N train station on July 17 when a thief grabbed his backpack and knocked him down.
The force of the grab sent both mother and son tumbling down the stairs.
Her son, Kyaw Zaw Hein, said he frantically yelled for help and there was a lot of blood.
Than, who worked as a seamstress making aprons, suffered a severe brain injury.
She was in a coma in the hospital for 11 days before her family made the decision to take her off life support.
The victims are from Burma and moved to New York City three years ago.
Following the crime, her son told Eyewitness News that he feared for his safety and was afraid to ride the subway.
"She meant the world to me," Hein said.
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