A Fairfield grandmother is behind bars Wednesday morning, after police say she intentionally drowned her grandson in her bathtub.

The Fairfield Police Department received "multiple 911 calls" Tuesday morning from homes surrounding the residence of 51-year-old Dawn Diana Raines-Hewes, FPD spokesperson Officer Cleo Mayoral says.

When officers arrived at the Raines-Hewes home at 10:51 a.m., they found an unresponsive 4-year-old boy, Mayoral says. Though emergency responders attempted to resuscitate the child, who they say was Raines-Hewes' grandson, they were not successful. He was pronounced dead at a local hospital, Mayoral says.

That's when "Major Crimes Unit detectives were dispatched to investigate" the child's death, and determined that he had been "intentionally drowned" in a bathtub in Raines-Hewes' home, Mayoral says. They arrested Raines-Hewes Tuesday evening, and booked her into the Solano County Jail on charges of murder.

According to Mayoral, officials have been in contact with the boy's mother, but they they are holding off on publicly releasing the name of the deceased child until they can confirm that the boy's father has also been notified.

The deceased 4-year-old was not the only grandchild at Raines-Hewes' home at the time of the drowning, Mayoral says, as Raines-Hewes' 1-year-old and 6-year-old granddaughters were also in her care when officers arrived. Both of those children were not injured and have been placed into protective custody.

“At this point," Mayoral told the Chron, "it’s best to keep the children apart from the other adults in the family."

"Information regarding a motive is not being released at this time," Mayoral said Wednesday morning.

"This is a very complex investigation and still in the early stages."

Raines-Hewes is currently being held without bail, Mayoral says. A date for her initial court appearance had not been set at publication time.