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A heartbroken California family was searching for answers Thursday after a pregnant 20-year-old mother was shot dead over the weekend with her 4-month-old son lying in bed next to her.

Police told KFSN several people were in the bedroom early Sunday morning when Amber Baker was shot inside her Fresno apartment, and investigators were trying to track them down.

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"A lot of people were here when we got here, and we've been working on the case since we got it that morning," Lt. Joe Gomez with the Fresno Police Dept. said.

Baker was about six weeks pregnant. Her father demanded the person or people responsible to come forward.

"We're not a rich family, but we're rich with values and love and compassion," Vance Baker told KSFN. "We believe that there's more good in this world than bad. We just got viciously attacked by the bad. Our main goal is to give my beautiful daughter justice."

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The apartment was shared by Baker, her son, her sister, Cassie, and three other women. Cassie Baker told the Fresno Bee that Amber had invited several people over for a party Saturday night. But after an argument, Cassie left.

“Our last words were so hateful,” she told the newspaper.

After sitting in her car, Cassie Baker said she sent her sister a Facebook message to apologize, but she got no response.

Then Baker got a phone call from a roommate who said Amber had been shot. The details of the shooting remain unclear, but Cassie Baker said Amber started acting differently before the shooting.

“Maybe it was the friends she started hanging out with,” she said.

Police told the Fresno Bee they were not ruling out gang involvement and asked anyone with information to call them.

A GoFundMe page has been set up to help with funeral costs.

“Amber had a zest for life, her smile was contagious,” the page read. “She brought laughter and smiles to all. Amber leaves behind a 4-month-old beautiful baby boy, Ayden. Her baby was the light of her life.”