Philadelphia police spokesman Frank Vanore says 18-year-old Patrick Johnson died after being stunned twice during a long confrontation Thursday with police.
Police say they had been to the northeast Philadelphia house more than a dozen times, and that Johnson brandished a butcher knife on a recent visit.
Vanore says Johnson had lit fire to some sticks and charged police Thursday. He says officers stunned Johnson once upstairs and later in the basement.
Philadelphia health department spokesman Jeff Moran says the autopsy may not be concluded Friday.
Police say Johnson had apparent mental-health issues.