The 21-year-old was employed at the time as an intern at a day-care centre in Kalmar, southern Sweden. His internship began on January 27th.
"He committed his first sexual assault the very same day," district prosecutor Linda Caneus said. "His last day was April 3rd, and that day he also perpetrated several assaults."
On Wednesday, he was handed a series of charges, including the aggravated rape of a four-year-old girl twice in one day at the day-care.
The charges saw the man pinned for nine cases of aggravated child rape, eight cases of aggravated child molestation, eight cases of aggravated exposure of children for sexual posing, and three cases of sexual molestation.
The man was also charged with aggravated child porn crimes, the Kalmar District Court said. He is believed to have secretly filmed the children with a phone or camera while they were in poses of a sexual nature.
Police confiscated just under 600 pictures and over 200 films from the man's computer. Around half of the images and films were deemed to be aggravated instances of child porn.
The man is suspected of using social media services including Skype to share 16 of the images, five of which were considered to be of an extreme nature.
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The man has already confessed to several of the molestations. Seventeen children were involved in the extensive investigation, all but two of whom were at the day care. The majority of the victims were between two and six years of age, and the youngest had not yet turned two.
A preliminary investigation has indicated that the man may suffer a serious psychiatric disturbance, something that a fuller investigation will determine next week.