( CNN ) -- A 17-year-old student was formally charged Tuesday with the kidnapping , sexual assault and murder of 10-year-old Jessica Ridgeway , whose body parts were found at a park in a Denver suburb earlier this month . Austin Reed Sigg , a student at Arapahoe Community College , was also charged with attempting to kidnap , sexually assault and murder a female jogger last May . The charges were outlined in a 17-count accusation filed by Jefferson County , Colorado , District Attorney Pam Russell Tuesday . Sigg , who lived about one mile from Ridgeway 's home in Westminster , was charged as an adult , a decision that could be challenged by his lawyers . The teen was arrested a week ago and accused of strangling Ridgeway , dismembering her and placing some of her body parts in a crawlspace under his family 's home . Police first found parts of her body at a park 5 miles away five days after the bespectacled blonde girl disappeared while walking to Witt Elementary School on October 5 . The big break in the investigation came last Tuesday night , when Sigg 's mother called 911 and handed him the phone . Sigg , police said , confessed . Along with charges related to Jessica 's death , Sigg is also accused in the May assault of a 22-year-old woman on a hiking trail . Suspect in Jessica Ridgeway death made girls in the area uneasy . CNN 's Shawn Nottingham contributed to this report .
Austin Reed Sigg allegedly strangled and raped her . He is also charged with conspiracy to kidnap , sexually assault and assault a jogger . He 's tried as an adult , a decision his lawyers could appeal . Police say Sigg confessed last week .