The 37-year-old man from Mirrabooka is alleged to have stabbed a four-year-old golden Labrador at the Apple Blossom Polyantha Reserve on Wednesday night.
He is due to appear in the Perth Magistrates Court on June 15 to face a charge of animal cruelty.
"Within a split second Luna was on the floor, I thought she was just submitting, wanting to play," the woman said.
"The man's bent down, I didn't hear any snarls, growl, yelps or barks, I thought everything was fine."
She jogged up to the man to make sure her dog was not bothering his small, tan-colored dog.
She said he put his hood on and mumbled something incoherent before he walked away, broke into a run and jumped a fence.
"I got closer, I realized she was on the floor, blood all over her, I just dropped and start screaming and screaming," she said.
"I picked her up and lay her on top of me and felt her heart and I couldn't feel her breathing, she was gone within seconds."
The woman rushed Luna to a nearby vet but she could not be saved.
She said her dog was gentle and good with other animals.
"She's our little baby, she sleeps on the bed with me … she was just beautiful," she said.
(ABC - May 20, 2017)