FRESNO, Calif. (CBS News) – A 20-year-old pregnant woman was found shot to death with her infant son lying next to her unharmed, reports CBS affiliate KGPE.

Police say they found the body of Amber Baker early on February 26. Baker’s sister, Katie Martin, told the station that she was found in bed with her 4-month-old lying beside her.

“Amber was a beautiful person, she had a huge heart,” said Martin, who told the station her sister was six weeks pregnant. An autopsy confirmed the woman was pregnant.

It was unclear from local reports whether police suspected foul play. Baker’s family said she was not involved in gangs or drugs, but police said they are looking at all angles to find out what exactly happened.

Baker worked at a local McDonalds.

According to the Fresno Bee, another sister, Cassie Baker, said that the night before the shooting, Amber had invited friends over to the apartment they shared with three other women, and the sisters had an argument. Cassie said she left with her son and later messaged her sister through Facebook, but never heard back.

Police told KGPE that several people were in the apartment when they found Amber’s body and they have been questioned, but the investigation is ongoing.

Police are asking anyone with information to call the Fresno Police Department or call Crime Stoppers at 559-498-STOP.