Mark Duenas was in court today after being arrested by the Shasta County Sheriff's Office on Friday and charged with the May murder of his wife Karen, a major development in a case that sparked national attention. He pleaded not guilty.

Duenas was already a person of interest in the case. Detectives said early in their investigation that he had cut all ties with the Sheriff's Office after being interviewed a few times.

Duenas' attorney said that he did not expect Duenas to post bail. The entire back room of the court room was filled with his supporters. His bail remains at $1 million and he will be back in court on Oct. 17.

According to an investigation summary contained within court documents filed Friday, and obtained by KRCR News Channel 7, prosecutors will likely rely heavily on a 911 call made on May 5, 2012, in which investigators say Mark Duenas admits to killing his wife, before saying there is "blood everywhere." The document indicates Duenas initially admitted to making that 911 call, but once it was played for him in its entirety by detectives, he denied the voice on the call was his.

The document also indicates a belief by detectives that, in the month leading up to Karen's death, Mark Duenas had, "reestablished an old relationship with a married woman in another state," and that when Karen found out about it, "she was angry and upset." The document indicates the other woman told investigators Mark had previously made the statement that, "'something bad would have to happen' for them to be together."

In a phone interview Friday afternoon, Mark Duenas' attorney, Ron Powell, called this development in the case "surprising," and said it "makes you wonder" what detectives "found now that they didn't have" when the crime occurred.

Duenas himself has previously denied killing his wife, including during an off-camera interview with KRCR News Channel 7 shortly after he was named a person of interest.

He is scheduled to be arraigned on Tuesday.

Karen Duenas was a mother of five and a teacher at Shasta College. She and Mark had been married for 33 years.