The attack occurred in the blink of an eye Wednesday night.
A choir member from the Greater Centennial A.M. E. Zion Church was stabbed on the church steps as she left practice.
It's an act of violence that shocked the Mayor of Mount Vernon who is a parishioner and friend of the victim.
53-year-old Sharon Winston was stabbed with such force, police say the knife blade broke off and impaled in her shoulder.
As Winston staggered back inside the church, the suspect ran away.
From the beginning, police suspected the victim's ex-boyfriend.
Early Friday morning, police arrested 38-year-old Jonathan Green who they say was trying to flee.
There have been prior domestic violence incidents involving Green and Winston.
But in this case, investigators credited the public for providing police several leads.