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Police tape blocks off a section of San Carlos Avenue as Alameda County Sheriff's deputies work on the scene at an overnight house fire where a woman's body was discovered inside in Castro Valley, Calif., on Thursday, Oct. 18, 2012. Investigators are looking into the suspicious fire. (Anda Chu/Staff)

SAN LEANDRO -- After two Hayward teens allegedly strangled a Castro Valley woman in her home last week, they went to lunch, saw some friends and returned later to set a fire and cover their tracks, police said Friday.

Christian Birdsall, 16, and Cody Nicosia, 18, were arrested Thursday and charged as adults in the Oct. 17 slaying of Barbara Latiolais in her Castro Valley home, said Alameda County Sheriff's Office Sgt. J.D. Nelson.

The slaying is "the kind of case nightmares are made of," Nelson said. "There's some absolute evil out there, and these two are evil for doing something like this."

The pair were arrested Thursday when police served a search warrant at a home on Rex Road in Hayward, where they were living with Nicosia's father, Nelson said. When investigators arrived, Nicosia's father became upset and told the teens, "If you did something, you need to come clean."

According to Nelson, Nicosia then looked his father in the eye and told him, "We killed someone."

The teens reportedly laid in wait the morning of Oct. 17 outside the home at 2431 San Carlos Ave., where Latiolais, 58, lived with her longtime partner, Michael J. Rice, 60, police said.

Latiolais, who neighbors described as a kind, peaceful woman, was alone in the home -- Rice was out of town -- and the pair waited for the woman to leave. When she didn't, Birdsall went to the door about noon and offered to do some work, Nelson said.

Birdsall had previously done yard work at the house and Latiolais knew him -- he is distantly related to Rice, and his mother was living with Rice's brother -- so Latiolais let him in. Once inside, Birdsall unlocked the back door for Nicosia, who entered the house, came up behind the woman and put her in a chokehold until she passed out, Nelson said. As they started taking items, she began making noises and came to, at which point they strangled her to death with a rope, he said.

The teens completed the burglary, left the home in the couple's Volvo, and went to lunch at a local restaurant, Nelson said. After meeting up with friends, they decided to return to the house to eliminate the evidence, police said.

About 10:30 p.m., the pair returned to the home, where they soaked Latiolais' body with gasoline and spread fuel around the house, police said. The pair threw a match through the front door and left close to midnight, according to police.

Fire crews found Latiolais' body while extinguishing the blaze.

Eyewitness description

The next morning, Birdsall took the stolen Volvo to Redwood High School, where he realized during his first-period class that he probably shouldn't be driving it, police said. He drove the car to Brookdale Boulevard in Castro Valley and ran back to school, where he was stopped by campus police for being tardy and asked to sign in -- a key piece of evidence used by detectives.

According to Nelson, it was when he abandoned the car that an eyewitness got a look at Birdsall. A description was provided to police to create a composite sketch of the person seen driving Latiolais' car, which was reported missing by investigators that morning.

After the sketch appeared in local media, a family member came forward and claimed that the sketch depicted their relative, Nelson said. The eyewitness identified a photo of Birdsall, prompting detectives to issue a search warrant of the Hayward home, where the teens were arrested in connection with the killing on Thursday.

Guns and money

A motive for the burglary came down to guns and money, and the pair had reportedly already sold some of the six to nine handguns and rifles taken from the home, Nelson said. Others were stashed in Hayward's Carlos Bee Park and have since been recovered.

Each of the boys claims to have taken only about $800 from the home, though investigators believe that amount to be higher, Nelson said. Detectives also say the teens knew they were entering the home to commit murder before Birdsall even knocked on the door.

"This woman was in the sanctity of her own home, and violated by someone she trusted," Nelson said. "It was just a despicable act. Why two teenagers would do something like this is beyond imagination."

When investigators called Rice to say that they had two suspects in custody, the retired firefighter broke down crying, Deputy Gus Mora said. "He is just absolutely devastated," Mora said. "She left behind a daughter, nieces, and a sister."

Birdsall had previously been arrested on suspicion of theft and Nicosia has no criminal history at all, police said.

Contact Erin Ivie at 925-847-2122. Follow her at Twitter.com/erin_ivie.