A blood trail leading TO the exit of the Aurora theater. Also see the white car where police found Holmes locked inside.
At a July 20 press conference Aurora police Chief Dan Oates said investigators were confident that James Holmes acted alone in the largest mass shooting in U.S. history by casualties and that authorities were "not looking for any other suspects."

But doubters are citing official evidence to question that Holmes was the only shooter, or a shooter at all.

The argument of the skeptics can be split into three categories: the discovery of Holmes, the real-time testimony on police radio transmissions and the extra evidence at the scene.

The discovery of Holmes

During the press conference, Oates said that Holmes was "apprehended outside his White Hyundai parked in the back of the theater" and that he "surrendered without any significant incident."

According to police radio transmissions (at 6:15), an officer found "a suspect in a gas mask" and another officer asked "Is that the dude in the white car you're by?" After a few transmissions, an officer asks (at 6:49) "That white car in the rear of the lot - is that a suspect?" The response is "Yes! We've got rifles, gas mask, he's detained right now, I've got an open door going into the theater."

Skeptics cite this exchange as evidence that Holmes was found in his locked car with a gas mask on and heavily drugged - not outside the car as Oates said - which would have forced first responders to break the passenger side window and get a white stretcher board in preparation to transport him.

The police radio transmissions

We've reported on the eye witness report from Corbin Dates, who said that it looked as if someone in the theater took a phone call by the emergency door and pried it open while "looking for somebody to come his way."

Another witness told a reporter: "From what we saw he wasn't alone ... because the second can of tear gas didn't come from his side."

Skeptics highlight that police radio transmissions seem to corroborate those accounts:

Three minutes after Holmes was supposedly detained in/by his car, an officer says (at 9:58): "One of the shooters might be wearing a white and blue plaid shirt" and the dispatcher responds "Copy, outstanding shooter possibly wearing a white and blue plaid shirt."

An officer says (at 11:43): "The suspect is saying that he's the only one but I'm getting conflicting suspect descriptions from the witnesses out here."

Then, the dispatcher receives several updates (at 24:42) and says: "Copy, all units ... male with a red backpack and another one possibly in black clothing headed toward Alameda" Avenue.

Subsequently an officer says (at 25:00): "Suspect is going to be male, unknown race, black camo-type outfit, believed to be wearing a vest, gas mask and multiple long guns." That update is reiterated by another officer at 31:15.

Even after 45 more minutes pass - making it more than an hour after Holmes was detained - the officers still mention other potential shooters:

1:16:16: Officer: "Talking to people making statements, sounds like we have possibly 2 shooters, one that was in Theater 8 seated, another one that came in from the outside into Theater 9. Sounds like it was a coordinated attack."

1:16:55:Dispatch: "Every unit, possible 2nd shooter still at large... Keep the media away from them."

1:31:27: Dispatch: Again, no witnesses are to be released, even if they've been spoken to."
The trail of blood leading toward (as opposed to away from) the emergency exit of Theater 9 is currently unexplained.
The extra evidence outside the theater

There has not yet been an official explanation of the orange duffel bag, gas can and ballistic gear found at a different part of the parking lot than the ballistic gear found near Holmes' car.

And although authorities say they found a 100-round, drum-style ammo clip in the rifle used by Holmes, skeptics note that the rifle found outside of the Theater 9 emergency exit appears to have a normal clip.

Another puzzling piece of evidence if Holmes was the only shooter is the second gas mask found at the far end of the parking lot, hundreds of feet from Theater 9's emergency exit and Holmes' car. (Holmes was found wearing a different gas mask.)

On July 20 Oates said police "immediately arrested the suspect at the back of the theater" 90 seconds after the first 911 call was made, which would make it difficult for Holmes to account for all of the items.

All that being said, the Arapahoe County Court judge has granted a request to seal the case against Holmes after the prosecutors argued that disclosing the court records would be "contrary to public interest" and "could jeopardize the ongoing investigation."

So we won't be able to compare the skeptical line of thinking with the search warrants, affidavits, orders and case file anytime soon.