Authorities charged a Cleveland mom with two counts of aggravated murder Tuesday after the father of her two young daughters found the girls "lifeless" in a bathtub of water, police said.

Amber Hill, 22, was arrested at her apartment after calling her husband to tell him that the children "are at peace," said Cleveland police Lt. Thomas Stacho. Hill remains in city jail on suicide watch.

A 2-year-old girl and her 4-year-old sister drowned, according to the county coroner, who ruled the deaths homicides.

Jamie Cintron, 23, the girls' father, told police he received a call at work from Hill, Stacho said.

"He received a phone call at work, rushed home and found both of the children lifeless in the bathtub of water," Stacho told FOXNews.com.

Cintron pulled the children from the tub and called 911.

"Both my daughters are laying here dead! Why? Why are my daughters dead?" a distraught Cintron told a 911 operator.

"My daughters are dead," Cintron repeated, "both of my daughters are dead!"

Click here to listen to the 911 calls.

Neighbors say the woman struggled with the pressures of being a mother and going to school.

Hill, who neighbors said was studying to be a nursing assistant, had no history of abusing or neglecting her children with the Cuyahoga County Department of Children and Family Services, The Plain Dealer reported in a story published Tuesday.

Deondra Hurt, 19, who lives in the same two-story apartment building, said Hill had taken good care of the children, ages 4 and 2.

"She always had her kids dressed up, with hair done every day," Hurt said. "She took care of them. They were well behaved kids. They played jump rope and would write on the ground with chalk."

Hurt said she heard the girls' father screaming and shouting. She later went to the apartment and saw Hill "on a couch, and she was just sitting there. She was a nice girl. It's real sad."

Hill provided only her name, age and address, but would not answer further questions at the apartment, Stacho said. She was calm and showed no emotion when she was taken away by police, he said.

"At this point she's our only suspect," he said.

Stacho said the girls were placed on life support by a city medical services crew and were pronounced dead at MetroHealth Medical Center.

FOX News' Jeff Goldblatt and The Associated Press contributed to this report.