Zak Bagans had convinced the girl's family to stay in the 'haunted' house so that he could film a documentary about it.
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As soon as they began filming, strange things began to happen; objects began moving by themselves, the mother of the family was kicked by an invisible force and strange noises made it difficult to sleep at night.
The worst was yet to come, however, when the family's little girl began having violent outbursts.
According to TMZ.com, she began 'threatening to hurt herself and others' and the family 'witnessed her speaking in tongues' - all of which, they say, are signs of demonic possession.
Zak revealed that they were forced to take the little girl to a Catholic priest, who performed an exorcism - and the ritual was recorded on video.
The girl, Zak claims, is now back to her old self.
Watch the video for yourself below:
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Filming was stopped until the little girl was on the mend - but Zak says he plans to finish the documentary this December.
Do you believe in ghosts? Let us know via the comments box below now.