According to a police source, the person of interest is an exterminator who had a job scheduled in the neighborhood and followed Ketunuti to her home.
At the man's house, a single two-story suburban residence that still displayed Christmas decorations and wire reindeer on the front lawn, investigators were scouring garbage cans Wednesday night as police helicopters hovered overhead. Police also towed his Ford F-150 truck. An investigator said officers were "looking for any link to her."
Neighbors said the man shared the house with his girlfriend, a young child, and the girlfriend's stepfather.
Ketunuti, 35, a pediatrician and researcher at Children's Hospital of Philadelphia, was found strangled, bound by rope, and set afire Monday in the basement of her rowhouse in the 1700 block of Naudain Street. Her killing has horrified neighbors on her quiet block, and set other Center City residents on edge.
Earlier Wednesday, Homicide Capt. James Clark said police had not determined if Ketunuti's killing was random or targeted.
This week investigators have worked around the clock retracing her steps, outlining how she spent her final hours, and narrowing the time of the killing to between 10:50 a.m., when she returned home from errands, and 11:50 a.m.
Members of the Homicide Task Force collected surveillance footage from cameras at a coffee shop, drugstore, and the hospital overlooking the block where she lived, and removed evidence from her house. Investigators also returned to the crime scene Wednesday.
Ketunuti lived with her pit bull/Lab mix, Pooch. Her boyfriend, Surya Mundluru, a doctor who lives in New York, assisted police inside Ketunuti's house Tuesday.
On Wednesday Clark said the victim's family members were still in Thailand, and were "making their way" to Philadelphia.
Also Wednesday, Councilman Kenyatta Johnson announced $15,000 in private donations for a reward for the arrest and conviction of a suspect, adding to the city's $20,000 police reward.
Johnson said he was in Washington for President Obama's second inauguration when he learned about Monday's "act of evil and wickedness" in his Philadelphia district.
"She specifically made a choice to pursue her career here in the city of Philadelphia," Johnson said of Ketunuti, who was pursuing a master of science in clinical epidemiology at the University of Pennsylvania's Perelman School of Medicine.
Contact Allison Steele at 215-854-2641 or firstname.lastname@example.org.