An Arizona mother accused of killing her two children found dead strapped in their car seats Monday night will face first-degree murder charges, police announced Tuesday.

Brittany Velasquez, 20, was charged after someone reportedly found her 2-year-old son and 10-month daughter dead in their car seats. Superior Interim Police Chief Christian Ensley said Tuesday that, before they arrived, the children were removed from the car seats so Velasquez could perform CPR.

As CrimeOnline previously reported, police said they charged Velasquez after finding evidence of foul play.

READ More: Infant and toddler found dead strapped to car seats; foul play suspected

Pinal County Sheriff’s Office Mark Lamb told reporters Tuesday that charges could change based on the results of pending autopsy and toxicology reports. Lamb said they received the go-ahead from Superior police to take on the investigation.

“We want to make sure we have the appropriate charging,” Lamb said, adding that he’s not aware of the children suffering gunshot or stab wounds.

Lamb declined to comment on the circumstances surrounding the children’s deaths, citing an ongoing investigation. However, Pinal County Public Information Officer Navideh Forghani revealed Tuesday that Velasquez was the one who placed the 911 call.

Local reporters with KSAZ revealed that the woman’s brother spoke to the station, claiming that he and his family reached out to police and CPS more than a dozen times to no avail. Relatives alleged that the mother would neglect her children.

He reportedly went on to describe his sister as “deranged” and a “great manipulator” who would deceive caseworkers who visited the home. The children’s home situation never changed after these CPS calls, he said.

Alarmingly, Ensley confirmed many of these claims Tuesday, revealing that CPS was called to the home as recently as January 3. In the last two years, police responded to the home seven or eight times, he said, though the nature of those calls was not immediately known.

READ More: Mother accused of murdering two children found dead in carseats lost her husband just after daughter’s birth: Reports

Ensley went on to reveal that it was an officer who placed the January 3 call and it appears that no action was taken on CPS’ part. At the time, police were called to the home for a theft. An officer was reportedly concerned for the children’s well being and contacted CPS.

He also said that a relative told police that Velasquez wasn’t watching the children. However, it’s unclear if that’s what prompted the January 3 CPS call or if someone other than Velasquez was responsible for watching the children.

The police chief called the situation “frustrating” and mentioned that it’s possible that authorities missed warning signs.

“This kind of thing doesn’t happen here,” he said, referring to the alleged murders. “It’s a devastating blow.”

[Featured Image: Brittany Velasquez/Pinal County Sheriff’s Office; Facebook]