Philadelphia (CNN) -- Andrew Cattaneo is still in shock.
It's been only a day since his neighbor across the street, Melissa Ketunuti, was found dead in the basement of her row home Monday afternoon, her hands and feet bound, her body set on fire.
Standing in the doorway of his home, Cattaneo watched as police detectives returned to the scene Tuesday while news reporters huddled nearby trying to stay warm on the blustery January afternoon.
"She was very pleasant, very nice, very friendly and quiet," Cattaneo said, looking across the street. "It's very upsetting."
Although authorities were awaiting the final autopsy report, Philadelphia Police Capt. James Clark, homicide commanding officer, said at a news conference Tuesday morning that Ketunuti, a 35-year-old physician, apparently was strangled. There were no immediately obvious signs of sexual assault, Clark said.
Ketunuti lived alone with her dog Pooch on a quiet, narrow and tree-lined street in Philadelphia's Center City. It was her dog walker, police said, who discovered her smoldering body.
The investigation is ongoing, Clark said, and the motive for her death is unclear. Police continued to canvass the neighborhood Tuesday in search of surveillance video.
Police say Ketunuti stopped at several stores Monday before making her way home, and there were no signs of struggle, indicating that she may have been followed.
"We don't know if she walked in on individuals inside of her property, we don't know if individuals forced her inside her property, or whether or not she knew her killer," Clark said. "We're not closing any avenues."
In 2008, Ketunuti moved from Washington to Philadelphia, where she was a pediatrics resident at the Children's Hospital of Philadelphia.
"This is hopefully the last move for at least 3 years, given that's how long it should take to finish a pediatrics residency," she penned on her personal online blog where she chronicled her globe-trekking adventures and updated her progress with school.
"As sexy as it was to be a life-saving surgeon, I feel much better suited for pediatrics," she wrote. Her postings referred to a surgery internship at Georgetown University Hospital in Washington, and a second internship in cardiothoracic surgery at a veterans hospital.
Across the street from Ketunuti's house, another neighbor who did not want to be identified was visibly upset at the news of her death.
"Who would want to do this?" the neighbor said.
The neighbor described Ketunuti as a private person, but not unfriendly.
"I'm struggling for the logic to why my friend is dead," the neighbor said, fighting back tears. "I'm sick with this."
The neighbor said Ketunuti was often seen running long distances, and returning home with groceries, that she had very few visitors, and that Ketunuti spent a significant amount of time at the hospital.
That was a point reiterated by police.
"She dedicated her whole life to being a doctor and helping kids with cancer," Clark said. "It's very unfortunate that she died in this manner."
Ketunuti graduated with a doctorate in medicine from Stanford University in 2007. Over the years, she completed a clerkship in Botswana, as well as internships at New York University and Johns Hopkins, she wrote on her blog.
No arrests had been made or suspects identified in the case as of Tuesday, according to police, and there is a $20,000 reward for arrest and conviction in relation to the killing.
Children's Hospital of Philadelphia released a statement Tuesday afternoon saying Ketunuti was a second-year infectious diseases fellow and researcher. She had been at the hospital for five years, the statement said, and had also served as a resident in the Department of Pediatrics.
"Melissa was a warm, caring, earnest, bright young woman with her whole future ahead of her," Dr. Paul Offit, chief of the hospital's division of infectious diseases, said in an e-mail statement.
"But more than that, she was admired, respected and loved by those with whom she worked here ... Her death will have a profound impact on those who worked with her and we will all miss her deeply."