Police face questions after a woman's body is found in a police van in Huntsville, Alabama

(CNN) Authorities in Huntsville, Alabama, are facing questions surrounding the discovery of a woman's body in the back of a rarely used police van in a police parking lot.

A police officer discovered the body of Christina Nance on October 7 in an unoccupied police van in the back corner of a parking lot at the Huntsville Public Safety Complex, Huntsville Deputy Police Chief DeWayne McCarver said in a news briefing Friday. Her family had reported her missing October 2.

"The officer noticed shoes next to the van and approached, discovering Ms. Nance's body inside. Windows on the van were observed to be opened and on this type of van they popped outward," he said.

McCarver told reporters it's department policy to keep those vans locked.

"All city vehicles should remain locked any time they are not in use or occupied," he said. "Sometimes, you just have to say that was something that shouldn't have happened. It did."

CNN has reached out to Nance's family and the Madison County Coroner's Office for comment.

Investigators have been poring over security footage from the parking lot trying to piece together what happened, McCarver said. Investigators eventually determined Nance entered the van September 25 around 12:30 p.m. (1:30 p.m. ET).

During the news conference, McCarver walked reporters through grainy surveillance footage, highlighting Nance's movements on September 25 and the days following as she opened and closed the windows of the van.

"Ms. Nance is observed in the video, walking around the parking lot" on the 25th, McCarver said. "She lays down in the bushes at some point (and) she sits on the hood of a police car for some time. She approaches other cars in the parking lot. ... And this all happens for about 10 minutes before she enters the van."

Investigators noted the last time Nance opened the windows, in what McCarver described as a very busy parking lot, was September 28, the deputy chief said.

"Cars go by, people walk nearby the van. We just wish that she would have hollered out to someone or something, because there were plenty of ... what we see as potential opportunities for this to not be a tragedy. And unfortunately, no one was able to realize she was in that van and that was the outcome," McCarver said. Officers are in and out of the lot 24 hours a day, seven days week, he added.

The van was purchased in 1995 as an inmate transport vehicle, McCarver said. It was repurposed by the department in the early 2000s for evidence transportation and has not been used since March, McCarver said. Because the vehicle was designed for inmate transport, once the back doors are closed, there is no way to open them from the inside.

McCarver said authorities at this point "have no idea of knowing what her state of mind was, what was going on there."

Madison County Coroner Dr. Tyler Berryhill said no foul play or bodily trauma was detected during an autopsy conducted October 12, a news release from the police department said

"The official cause of death will be ruled by the State Medical Examiner once additional studies, including toxicology, are complete," the release says.

The Huntsville Police Department has come under scrutiny as Nance's family and advocates question how and why she was able to remain undetected inside an official vehicle parked in such a highly trafficked area for 12 days.

McCarver said police have treated this as a criminal investigation from the beginning and that investigators were initially delayed by the family giving an incorrect date for the last time they said they saw Nance.

McCarver also said the department's Crisis Intervention Team (CIT) officers "know her pretty well."

"They have worked with her in the past to provide resources and different things," he said. "We are familiar with her -- very familiar with her."

The family was able to view the surveillance video Friday ahead of the media briefing, McCarver said, reiterating the department is committed to working through this loss alongside Nance's family.

"The video was not clear enough to indicate that that was our sister Christina Nance," Nance's sister Whitney Nance told CNN affiliate WAFF. "It was just very heartbreaking to know that we didn't get the clarification that we really needed, that we wanted."

Civil rights attorney Ben Crump -- who has represented the families of George Floyd and Breonna Taylor, among other Black victims who suffered excessive force by the police -- issued a news release October 13 announcing he would be representing the Nance family as the investigation unfolds.

"We will get to the truth of what happened to Christina Nance, the young Black woman found dead in the police van in front of the Huntsville Police Department. We lift up Christina's family with prayer as they mourn this devastating loss," Crump said.