The family of a 31-year-old real estate agent found dead in her Los Angeles apartment suspected something was awry when their iPhone messages to her suddenly turned green, indicating that they hadn't been received.

Maleesa Mooney’s family had been unable to reach her since last Thursday, when they contacted police, her younger sister Jourdin Pauline told Fox News Digital on Friday. A group of friends were in her apartment, Pauline said. "Her friends left, but she was still there."

After Mooney’s family contacted police, an LAPD officer was sent to her residence on South Figueroa Street on Sunday. The officer left a card on the door when no one answered. 

"They didn’t go in, they just left a card," Pauline said. "When we went to go check on her, the card was still there."

That day, according to Mooney’s bereaved sister, text messages that had been unreceived suddenly turned blue and delivered.

"Her phone got alerted that it was on, and her text messages were delivering – it was whoever had her belongings was trying to sell them and had access," Pauline said. "That gave us hope. We were thinking she was OK when the messages were delivering."

Police didn’t return until the following Tuesday. The building’s maintenance department let them into the "flooded" apartment where Mooney was found dead around 4 p.m., Pauline said, though it was unclear how the apartment flooded.

"If [this] case unravels, I’m sure things are going to come out," Pauline told Fox.

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Los Angeles Police Detective David Marcinek told Fox News Digital that Mooney's death is being investigated as a homicide, but that the Los Angeles Medical Examiner has yet to determine her cause of death. 

He declined to share specifics regarding Mooney's injuries or whether a suspect had been identified at press time.

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Pauline described Mooney as the "most amazing girl ever."

"She loved to cook, she was very nice, very sweet genuine person," she said on Friday. "She would ask a stranger how their day was going – just a very sweet, open-hearted person. She was very funny, very goofy. She could make a whole room laugh. And smart, and was very, very smart."

Although she dabbled in freelance modeling, Mooney primarily worked as a real estate agent with NestSeekers International. 

"She was showing million-dollar homes and was in the process of closing a few," Pauline said.

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In an Instagram post featuring the hashtag #JUSTICEFORMALEESA, Pauline pleaded for answers and mourned her beloved older sister. 

"Never in a million years did I think I'd have to make this post and get justice for my one & only sister... my heart is crushed I can't believe you won't be here with us anymore," she wrote. "This is so sick I can't believe my big baby sister is gone ... we will get justice for you my sister I promise you won't be gone in vain!"

Residents of the Skye at Bunker Hill Apartments complex were shaken by the grim discovery.

"It is scary," Kristin Verdiun told KABC. "I'm just right down the hall."