Police photo of Raghunandan Yandamuri

Police in Pennsylvania have arrested a suspect in the kidnapping and killing of a 10-month old girl and the slaying of her grandmother who was taking care of her in a Philadelphia suburb. According to the affadavit for his arrest, Raghunandan Yandamuri, after telling police he committed the crime, asked police to say his wife turned him so she could claim a cash reward being offered for the child's return.

The body of the baby, Saanvi Venna, was discovered overnight, police said Friday. Her grandmother Satyavathi Venna, 61, was found slain on Monday in the family's apartment in King of Prussia, about 15 miles north of Philadelphia and it was then that the baby was discovered missing.

Yandamuri, 26, an acquaintance of the family who lives in the same apartment complex, faces charges of first and second degree murder, kidnapping and burglary in what police say appears to have been a kidnapping for ransom that went awry.

Near the body of the grandmother, who died from stab wounds to her neck and chest, investigators found a ransom note demanding $50,000 for the return of Saavni, investigators revealed on Friday.

"If you want your daughter alive and safe, follow our instructions carefully," said the message, which is attached as an exhibit to the criminal complaint provided by police. It called for the baby's mother to deliver the $50,000 by 8 p.m. the same day, and warned, "Any cunning act from anyone of you will lead to your daughter's death."

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Investigators issued an Amber Alert just before 5 p.m. Monday after the child's father and slain victim's son, Venkata Konda Siva Venna, found the woman's body and realized his daughter was missing.

Police say Venna left work to check on the pair after receiving a call from a worried relative who was unable to reach them.

The baby’s mother, Chenchu Latha Punuru, was at work when Venna was killed and the child was taken, police said.

Pennsylvania State Police via AP Saanvi Venna, 10 months old, in an undated photo provided by police. Police issued an Amber Alert for her on Monday after her grandmother, who had been babysitting, was found slain and the baby missing.

In the ransom note, the writer used the nicknames "Shiva" and "Lata" for Saanvi's parents, which were known only to a handful of people, all of whom were in the community of Asian Indian Americans, according to an affidavit for Yandamuri's arrest.

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One of the people who knew those names was Yandamuri, who first told detectives he had no idea who had killed Satyavathi or taken Saanvi. He had attended a vigil held for the child and helped create and distribute missing child posters of the girl, it said.

Later in the interview on Thursday, Yandamuri said he was responsible for both deaths. He said he targeted the family because he believed they had money, and said his intention was to hide the child until the ransom was paid, the affidavit said.

According to the document, he told police he had stabbed the grandmother with a kitchen knife in a tussle for the child, stuffed a handkerchief into the child's mouth to stop her from crying, and then put her in a blue suitcase, which he later abandoned in a sauna at the apartment complex gym.

Following Yandamuri's description, investigators went to the sauna, the affidavit said.

"Hidden inside a dark wooden sauna under a deep bench, they found the lifeless body of Saanvi Venna. There was apparent blood on her white dress."

The grandmother had been visiting from India since July, authorities said, and was planning to return in January.

A reward for information leading to the safe return of the child had jumped from $30,000 to $50,000 on Thursday.

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