Tumblr user Illuminology points to the same confusion around the shooter's ID Friday morning and connects it to mixed reports of which weapons were found by the police:

According to multiple eyewitness reports from Aurora, Colorado, including at least one caught on camera by mainstream media news reports in Colorado, James Holmes did not operate alone... But the media quickly eliminated any mention of a second shooter from its coverage, resorting to the typical cover story of a “lone gunman.” Today, the exact same thing is happening with the Newton, CT school shooting.

Youtube user PathocracyNow has a video interviewing a Newtown resident claiming to have seen a second shooter. In the video's description:

It is clear that 20-year-old Adam Lanza could not have done this all by himself (assuming he was actually involved - we have no way of knowing and no way of ever finding out for sure). The shooting dead of 28 people, with at least 100 rounds let off, took place within three minutes... and we're being asked to believe that "autistic, troubled" Lanza pulled it off with two handguns?