A suspect's mother inadvertently helped police arrest the man they say robbed two women at knifepoint inside a Manhattan subway station.
34-year-old Kevin Williams of Harlem is being charged with two counts of robbery.
Sources tell us his mother recognized him in this surveillance video and told a friend, who then reported it to police.
Both incidents took place on the C and E train platform at the Spring Street station in SoHo.
Police say the latest happened around 11 a.m. last Saturday, when Williams grabbed a 49-year-old victim from behind.
They say he covered her nose and mouth with a white cloth and then pulled out a knife.
They say victim dropped her purse, and that's when Williams took $75 and ran off.
Police say he did the same thing four days earlier to a 50-year-old woman, making off with $70.
No one was injured in either incident.