A fifth person was arrested Wednesday in connection with the killing of two mothers in Oklahoma, officials said.

Paul Grice, 31, was arrested and booked into the Texas County Jail on two counts of first-degree murder, two counts of kidnapping, and one count of conspiracy to commit murder in the first degree, the Oklahoma State Bureau of Investigation said in a press release.

Veronica Butler, 27, and 39-year-old Jilian Kelley disappeared on March 30 while on their way from Kansas to pick up Butler's children from a birthday party in nearby Oklahoma. Their remains were found on April 14 after having last been seen together in a vehicle that was later found abandoned by the highway in a rural part of Texas County. 

Four people had already been arrested and charged with murder in connection with the women's murders. Tad Bert Cullum, 43, Tifany Machel Adams, 54, Cole Earl Twombly, 50, and Cora Twombly, 44, were all arrested on April 14, the bureau said. 

According to an unsealed affidavit, Adams is the paternal grandmother of Butler's children and the two were involved in a custody battle. Callum and Adams were in a relationship, according to the affidavit. 

According to authorities, all five suspects belong to an anti-government group called "God's Misfits" that regularly met at the Twomblys' home and other locations. The group had allegedly tried to kill Butler before, according to a teenage witness who spoke to investigators, who also said they were responsible for the murders, according to the affidavit.

A judge last week entered not guilty pleas for all four suspects in addition to denying them bond. 

Family members of the deceased were at the courthouse to confront Butler and Kelley's alleged killers. Bryson Butler, Veronica Butler's younger brother, told CBS affiliate KFDA that he hoped "justice is served."

"How can you hate somebody so much that you want to kill them? How can you hate the mother of your grandchildren so much that you want to end her life?" Butler's aunt told KFDA. 

—Jordan Freiman contributed reporting.

S. Dev

S. Dev is a news editor for CBSNews.com.