A woman working a second job as a dog walker was fatally stabbed by a stranger Tuesday as she was taking the dog back to its apartment, police said.

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A couple living nearby heard Margery Magill's cries for help, ran outside and immediately found the dog sitting and howling and Magill's bloodied body nearby, the Washington Post reported.

They administered life-saving techniques while emergency responders arrived. Magill, 27, was taken to a hospital and pronounced dead.

Eliyas Aregahegne, 24, was arrested and charged Wednesday with first-degree murder while armed, according to police.

Investigators said the two were apparently strangers. Aregahegne's motive is unclear, and investigators are trying to determine if he has mental health issues, NBC News reported.

"(She was) minding her own business, and somebody just decided to attack her," her father, Jeffrey Magill, told the Post. "I don't know how you get a handle on somebody doing something like that."

Magill was an avid traveler and had recently completed a master’s degree in international relations.