(PHILADELPHIA) -- Philadelphia-area exterminator Joseph Smith was arrested and charged on Thursday in the strangling and burning death of pediatrician Melissa Ketunuti.
Smith, 36, had been sent to Ketunuti's home on a service call, where the two got into "some kind of argument" in Ketunuti's basement on Monday, Capt. James Clark of the Philadelphia police department said Thursday morning.
"At her home they go into argument. It went terribly wrong. He struck her, and knocked her down," Clark said. "Immediately he jumped on top of her, started strangling her. She passed out, and then he set her body on fire."
The developments came after investigators collected hours of surveillance video and canvassed the neighborhood where police on Monday found Ketunuti's body. Ketunuti, 35, was a doctor at Children's Hospital of Philadelphia.
A silver Ford truck was towed from Smith's Levittown home, which was the same truck spotted on surveillance video Monday in Ketunuti's neighborhood, sources told ABC News affiliate WPVI.
Smith was spotted on video getting out of the vehicle and following Ketunuti to her home. The man left her home after an hour and was seen on video circling her home, sources told WPVI.
Ketunuti's body was found Monday in the basement of her Graduate Hospital-area row house after her dog walker called 911. Her wrists and ankles were bound behind her back, and she was on fire, police said.
The pediatrician was fully clothed and there were no signs of sexual assault, sources said.
Clark said she was strangled with a rope.
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