Melanie Breckle was working hard to build a better life.

The 23-year-old single mother recently graduated with honors from a business school, all the while working part time and caring for her 5-year-old daughter, said her mother, Rose Voisey.

Her family has no idea why someone would kill her.

Firefighters found Breckle's body about noon Tuesday in her father's burning apartment in the 400 block of May Valley, near Fenton. St. Louis County police said her death was a homicide, with the fire set afterward to hide clues.

The medical examiner was still trying to determine the cause of death. Investigators declined to discuss what were described only as "several injuries."

Detectives said Wednesday they have cleared Breckle's father, boyfriend and the father of her child from suspicion.

Family said Breckle split her time between her father's apartment and her mother's house in the 200 block of Viehl Avenue in south St. Louis County.

Voisey said relatives can't understand why anyone would hurt her daughter.

"She was an outgoing, beautiful, bubbly and intelligent woman," Voisey said. "She was just fantastic."

As a teenager, Breckle struggled with her parents' divorce and dropped out of high school, Voisey said. But she earned a high school equivalency certificate and put her education back on track.

"She had a lot of adversity in her life," Voisey said. "But she pulled herself up by the bootstraps."

Breckle recently graduated from Hickey College with a degree in accounting. She was looking for a job and stable life for her daughter, Jasmine.

"She was trying to hard to better herself," Voisey said. "She just wanted to make a difference in this world."