Inset: Marlene Vidal (Bexar County Sheriff's Office). Background: A burned out car allegedly belonging to Vidal in a parking lot in San Antonio, Tex. (WOAI).

A Texas woman is behind bars after two young children, believed to be 5 and 7 years old, were found dead inside a burned-out vehicle.

Marlene Vidal, 34, stands accused of two counts of capital murder of a person under 10 years of age and one count of arson, according to the Bexar County Sheriff's Office.

The underlying incident occurred during the early morning hours in a warehouse parking lot on Richland Hills Drive in San Antonio.

Sometime after 5 a.m. on Friday, a witness who was out walking their dog called 911 to report the car ablaze – after making contact with a woman there who claimed she had already called authorities, the San Antonio Police Department announced during a press conference.

Officers and firefighters arrived on the scene and extinguished the burning white Hyundai, police said. Inside the car, investigators found the victims and are currently working to identify them.

Vidal was quickly identified and arrested, according to police. The defendant is said to hail from Edinburg – a large city in the Rio Grande Valley located some 230 miles due south of the Alamo City. Police said she has "family connections" in the San Antonio area.

"At this stage of the investigation, we have statements made by the suspect, along with surveillance video and evidence from the scene that indicate she was solely responsible for the death of these two children," Assistant San Antonio Police Chief Jesus Salame Jr. said.

The defendant, however, was not immediately booked into the Bexar County Jail after her arrest, Law&Crime has learned. Vidal was finally booked and processed by jail officials late Friday evening.

"She just indicated that she was the one that we would be looking for," Salame added, describing comments Vidal allegedly made to police.

Law enforcement further described the 7-year-old victim as a girl and the 5-year-old victim as a boy who is said to be both autistic and nonverbal, according to San Antonio-based NBC affiliate WOAI.

The TV station spoke with the children's father who no longer lives with Vidal. He said he was devastated by the news of their deaths and confirmed the little boy had an autism diagnosis.

A motive for the slayings is, as of yet, elusive. Law enforcement have said mental health issues "may have played a role."

"So what I'll commit to you now is that we're going to continue working to find the truth, seek justice for these children, and support everyone affected by this tragedy," Salame said. "Everyone's going to want to know why something like this happened, and unfortunately, the why is sometimes the hardest question to answer."

The investigation is ongoing as police speak with family members "and others connected to the case," police said.

The defendant was arraigned on Friday night and appeared before a judge. When her murder charges were read out, Vidal audibly broke into tears and asked when her trial would start, WOAI reported.