A suburban pest exterminator has been charged with strangling a young Philadelphia doctor found bound and burned in her home, police have announced.
Jason Smith, 36, was charged with murder, arson, abuse of a corpse and risking a catastrophe in the slaying of 35-year-old Dr Melissa Ketunuti.
Homicide unit Captain James Clark said Smith was subcontracted to Dr Ketunuti's home after she requested an exterminator to inspect her home.
"They got into some type of argument. It went terribly wrong," said Capt Clark, who would not elaborate on the substance of the fatal disagreement.
He said Smith "struck her while she was in the basement, knocked her down, strangled her to death and ultimately set her body on fire" in an apparent attempt to hide evidence.
Smith, who has no prior criminal record other than "minor traffic offences", was arrested at his home in Levittown, about 25 miles northeast of Philadelphia.
Police said there were no signs of sexual assault and nothing was stolen from the home of the victim, whose body was bound with rope at her wrists and ankles and wrapped around her neck.
Investigators said Smith, who lived with his long-time girlfriend and her young child, and Dr Ketunuti, a second-year infectious-diseases fellow and researcher at the renowned Children's Hospital of Philadelphia, had never met before.
"It's very tragic," Capt Clark said. "You have a young physician who dedicated her life to helping people and to die in this tragic manner, it's very, very sad."
Dr Ketunuti, who had been having a problem with rodents in her house, was running errands around the neighbourhood just before meeting up with the exterminator, Capt Clark said.
He said detectives watched hours of surveillance video from nearby businesses, one of which shows Smith entering Dr Ketunuti's home with a work bag and dressed in a coat and gloves, then leaving without a coat under an hour later.
Other video shows the suspect getting into his truck after the slaying and driving past her home several times, Capt Clark said.
Dr Ketunuti's parents are in the process of making arrangements to travel from their home in Thailand to Philadelphia.