PHOENIX — A mother has been arrested after three young children were found dead at a home in Phoenix.

Phoenix police were called to the home near 24th Street and Southern Avenue around 7:25 p.m. on Monday, Jan. 20, for an "unknown trouble" call.

Police say when officers arrived, they were met by the mother, father, and another relative. When officers went inside the home, they found three kids unresponsive in a front living room area.

Officers attempted to perform CPR before fire crews arrived and pronounced the 3-year-old boy, 1-year-old girl, and 7-month-old girl dead.

Police say the three children have been identified as:

Zane Henry, three-year-old male

Miraya Henry, one-year-old female (she would have turned 2 next week)

Catalaya Rios, seven-month-old female

Police say the mother, 22-year-old Rachel Henry, told officers the children had been sick before she later admitted to killing them.

According to court paperwork, Henry told police that she suffocated the children and laid them on the couch to make it look like they were sleeping.

On Tuesday morning, police say Henry was arrested. She was booked into jail on three charges of first-degree murder. Watch the video in the player below to see Henry's Tuesday morning arrival to the 4th Avenue Jail.

Rachel Henry arrives at 4th Avenue Jail after death of three children

Henry’s next-door neighbor spoke to ABC15 and said she saw the young mom talking to police Monday night and thought there was something off about her.

"She looked nervous. I looked at her. As a mom, I would've been devastated. I would've been beating myself up seeing the tragedy that had just happened," said Miriam Soto.

Soto said she’d often see the three little kids playing outside, though she didn’t know the family well. Police say Henry recently moved to Arizona from Oklahoma.

Court documents state one of the people police interviewed said, "Rachel had a methamphetamine addiction and had been acting strange the past several days."

Catelin Klug tells ABC15 she met Henry a few months ago and the two would often talk.

"She would not stop talking about her kids, her kids, her kids," said Klug. "She would see something and say, 'Oh, my kids would like that.'"

Klug isn't sure what caused her friend to snap.

"I just want to know why," Klug said. "It doesn't seem possible to me that she would do that to them, the way she spoke of them."

Phoenix Fire spokesman Rob McDade said the firefighters who responded to the call Monday were sent home early to be with their families after such a traumatic scene. Their shift was supposed to end on Tuesday.

"This is one of the most difficult calls that officers and fire respond to, ones dealing with young ones who have lost their lives," Phoenix Police Sgt. Mercedes Fortune said.

During her IA appearance, the judge says that Henry had her children taken away when she lived in Oklahoma due to drug involvement. ABC15 reached out to the Oklahoma Department of Health Services to try to obtain additional information on what happened in the previous cases. Here is their response:

"We are devastated to learn of the deaths of these three children. However, the information requested is confidential under Oklahoma statute. The Oklahoma Department of Human Services is not investigating the deaths of the children involved. The investigation is being conducted by Arizona law enforcement. Oklahoma's death and near-death release statute is found at Title 10A O.S. 1-6-105 [oscn.net] and the confidentiality statute is found at Title 10A O.S. 1-6-102 [oscn.net]."