Ursula & Sabina Eriksson
The more you learn about this story, the more horrifying it gets.

Watch the documentary (Link Updated): http://www.youtube.com/watch?v=UHH0bysjkpM

This insane story brings to mind a few thoughts on explanations: 

• Brief insanity

• DARPA’s $2 billion yearly budget to create genetically altered human super soldiers

• MK-Ultra mind control victims

• Demonic possession

Wikipedia excerpt:

Ursula and Sabina Eriksson, born 1967, are a pair of Swedish twins who came to national attention in the United Kingdom in 2008 after an apparent episode of folie à deux which resulted in an incident on the M6 motorway, which was filmed on CCTV, and the killing of Glenn Hollinshead. No drugs or alcohol were involved in any of the incidents.[1][2] Their actions have never been explained, other than by a rare, induced delusional disorder which caused the pair to be temporarily insane.[3]

The twins met in Ireland before travelling to England. After their odd behaviour caused them to be left at an M6 service station, they ran on to the motorway numerous times and were struck by oncoming vehicles, causing Ursula to be incapacitated. Sabina refused medical aid and attacked a police officer, at which point she was arrested. After being released by police in Stoke-on-Trent, Sabina then was taken in by a local resident whom she later killed in an unprovoked attack. She was arrested after jumping off a bridge into a busy road and later pleaded guilty to manslaughter with diminished responsibility. She was sentenced to five years imprisonment and released on parole in 2011. Her whereabouts are currently unknown.