A violent kidnapping that ended with the murder of a 3-week-old baby girl took an even more sordid turn when police announced they had arrested a California woman who they said plotted to steal infants and pass them off as her own.

In arresting the woman and three others Wednesday, police in Long Beach and El Segundo said they had cracked a sinister scheme that led not only to the kidnapping and murder of tiny Eliza Delacruz in January, but also to an assault on a 23-year-old mother at a hotel in El Segundo last month who was targeted for her 4-month-old son.

Investigators in both cities would not say how baby Eliza died and declined to discuss what may have motivated the woman's three alleged accomplices to participate beyond saying that the man who they believe carried out the attacks was a friend and the other woman arrested was her daughter.

Long Beach Police Chief Robert Luna said his staff suggested avoiding the word "evil" to describe the case, but he couldn't.

"I can't summarize it any other way," he said. "In my 29 years, I've never seen anything like this. We've never seen anything like this where someone goes out looking for babies and they attempt to kill the mothers. It's just unbelievable."

Giseleangelique Rene D'Milian, 47, of Thousand Oaks, was arrested on suspicion of murder, kidnapping, attempted murder and conspiracy. Her alleged accomplice, 29-year-old Anthony McCall, of Oceanside, was arrested on the same charges.

Two others — D'Milian's 30-year-old daughter Charisse Shelton and 44-year-old Todd Boudreaux — were arrested on suspicion of helping cover up the crimes after the fact, authorities said.

All were being held without bail except Shelton, whose bail was set at $1 million.

The four are expected to make a first court appearance Friday. It wasn't clear late Wednesday if they had already retained attorneys or would request a public defender on Friday.

Eliza's mother, father and uncle were shot in their home on Jan. 3 and Eliza was kidnapped by McCall just two hours after he and D'Milian tailed a public bus that was carrying the baby and her mother, police said.

Eliza's body was discovered the following day in a trash bin in Imperial Beach, a city on the Mexican border about 100 miles to the south.

A second woman was beaten with a baseball bat on Feb. 6 in El Segundo, about 20 miles to the north, while her 4-month-old son was in the room and police now believe the child was the target of the same kidnapping scheme.

The mother was saved when hotel employees interrupted the assault but McCall escaped, said El Segundo Police Chief Mitch Tavera.

D'Milian also started a fake charity focusing on 1- to 2-month-old babies and asked her friends and acquaintances to spread the word by text message and phone calls in an attempt to get access to other children she could kidnap, authorities said.

D'Milian may have identified Eliza's mother through that network, police said, but the mother told police she'd never seen D'Milian before.

Police asked any woman with young infants who'd been contacted about such a charity to call police — although they don't believe there were any other victims.

There is no indication that D'Milian's married boyfriend — who lives somewhere in California and also has his own children — knew of the plot, said Long Beach Lt. Lloyd Cox.

D'Milian told him the twins had been born when she was out of the country.

"She fabricated a story and wanted him to believe these children were his. Why? We don't know. We're not sure what the motivation was," he said, adding that D'Milian was searching for children with a dark complexion that matched her own.

The case stumped Long Beach authorities for weeks because Eliza's parents and uncle were too severely wounded to be interviewed, Luna said.

When her mother recovered, she recalled that a woman pulled over in a black Range Rover she got off the bus on Jan. 3 and asked her about the baby girl.

Police last week released composite sketches of the woman and the kidnapper and released surveillance video of the SUV. The information generated tips and new witnesses who told police the location of the Range Rover and gave them names that matched exactly with suspects that the El Segundo police were already looking at in their assault case, Luna said.