Police in Aurora, Colorado, early on Sunday dismissed suspicions that another person helped James Holmes prepare the massacre at a movie theatre that left 12 people dead.
"There are multiple unconfirmed and inaccurate news reports about a second suspect," police spokeswoman Cassidee Carson said in a statement.
"In regards to those reports: An associate of Holmes was interviewed this evening. There is no reason to believe that he is involved."
She said further details of this investigation will not be released now.
Early on Friday, a black-clad gunman in full body armor opened fire at a packed movie theatre in Aurora, creating a bloodbath which left at least 12 dead and 58 injured.
He tossed two tear gas or smoke grenades into the audience at a midnight showing of The Dark Knight Rises, then gunned down terrified patrons as they scrambled for the exits.
Police arrested the suspect - identified as 24-year-old James Holmes - without encountering resistance by his car at the rear of the theatre in Aurora, a suburb of the city of Denver.
The denial followed media reports that police was looking for a possible second person, a fellow medical PhD student, who allegedly helped Holmes in his killing spree.
According to these reports, the man had allegedly called the police and threatened more violence if Holmes was not released. - Sapa-AFP