Police are searching the Kansas City area Wednesday for a couple accused of raping, beating and strangling a 41-year-old woman and burying her in a shallow grave.

Richard Davis and Dena Riley of Independence, Mo., have been on the run since Friday when police discovered a videotape of the deadly assault of Marsha Spicer in the couple's apartment.

"These are two of the most violent people that I think we have that are currently at large within the state of Missouri," said Michael Sanders, the prosecuting attorney in Jackson County, Mo. "On top of that, I think they're becoming increasingly desperate ... they don't have large amounts of cash.

"As this goes on, I think they're going to get more and more dangerous, more and more desperate, and that's why it's critical we get them into custody as soon as possible so other people aren't injured."

The couple was sighted Sunday in Perryville, Mo., at the Hilltop Apartment Complex, FOX News has learned.

“Until I heard the newscast I really didn’t realize what they’d done,” said Julie McAlister, who lives in the complex. “They had contacted a lady that lived here and came out looking for refuge but she told them that she couldn’t hide them here. They did stay for a few minutes. The police were here and they left.”

Police found Spicer's naked body in a shallow grave in Lafayette County on May 15.

“There’s no indication she was buried alive,” Kerrick Alumbaugh, the sheriff of Lafayette County, told FOX News. “She was dead before she was placed in the grave site.”

The couple was interviewed by police last week — before the tape was obtained Friday through a search warrant — but have since fled.

"Their whereabouts are totally unknown," said Independence police Capt. Ken Jarnagin.

Detectives noted that the couple had a camcorder aimed at their bed when officers interviewed them. Both denied knowing Spicer. Police believe the couple lured the victim to their home for a sexual encounter.

"It appears like initially the encounter was consensual, I don't think there's any question about it, that's what's shown on the tape," Sanders said. "But at some point, it became dramatically no longer consensual, when they tape her, duct tape her, strike and beat her."

According to the victim’s older sister, Jackie Schumacher, Spicer had known the couple for two years.

"It's just a group they all ran around with," Schumacher told FOX News. "I just didn’t have a clue it was anything like this."

Schumacher said her sister was very trusting and that "she would do anything for anybody."

Authorities say the tape recovered from the apartment of Davis and Riley shows the couple with Spicer in the violent final moments of her life.

Police say the video found on a TV stand in the couple's bedroom shows the 41-year-old Spicer with duct tape over her eyes and her hands secured behind her back. She is beaten, raped and sodomized as she pleads for the attack to stop.

Davis, 41, and Riley, 39, are each charged with first-degree murder, first-degree assault, kidnapping, forcible rape and two counts of forcible sodomy.

Davis is on parole after spending nearly 18 years in prison for a rape and sodomy conviction in 1987 in Lafayette County. According to a report in The Kansas City Star, Davis was paroled a year ago Wednesday from a Bonne Terre, Mo., prison. He married a woman in 2001 while in prison, but they divorced in 2004, the paper reported.

The couple’s neighbors are shocked by the allegations.

“I just never had any idea that something of that nature and magnitude ever took place,” said Ed Cable, who has lived in the neighborhood for nearly 30 years.

FOXNews.com's Sara Bonisteel and The Associated Press contributed to this report.