A 90-year-old California man has been arrested in the murder of his stepdaughter, whose Fitbit apparently aided investigators in identifying her stepfather as a suspect, officials said.

Karen Navarra was found dead in her San Jose home by officers responding to a welfare check on Sept. 13, San Jose police said.

Navarra, 67, had suffered a large laceration on her neck and a deep laceration on her head, according to the statements of facts written by police and provided by the Santa Clara District Attorney’s office to ABC News.