She was shot 22 times on Jan. 11, allegedly by her ex-boyfriend, Frank Deleon Jr., according to HPD.
Deleon was arrested on Monday and bonded out of jail in less than 48 hours.
Alvarez's mother says Houston isn't safe with Deleon back on the streets.
As Anna Machado prepares to bury her 15-year-old daughter, she says it hasn't totally hit her that she's gone.
"Happy. Full of life. With her nonsense. With her happiness. With her smile," Machado described Alvarez.
Alvarez was shot 22 times while walking her dog, "Peanut."
ORIGINAL STORY: 15-year-old girl shot and killed as she walked dog in SW Houston
Investigators believe her killer is 17-year-old Deleon.
He reportedly texted Alvarez to meet in her southwest Houston neighborhood the night of her murder.
Alvarez had been upset after finding out that Deleon was involved with another girl. Prosecutors say Deleon begged Alvarez not to tell anyone about their relationship, but she was angry.
Machado says she doesn't want to hear the details about what happened. She can't bear it. Instead, she's is focused on one thing -- getting Deleon back in jail.
SEE ALSO: 17-year-old boyfriend charged with murder of 15-year-old girl in SW Houston posts $250K bond
He got out less than 48 hours after being arrested and paying his $250,000 bond.
Alvarez's family said Deleon lives with his parents, in the same neighborhood as them, just a few blocks away.
For perspective, his bond was set high. On average, people charged with murder get about a $50,000 bond, a legal analyst told ABC13.
"I was in shock. I couldn't believe it. I still can't believe it. Why are you letting loose a monster like that? Someone that just executed someone. A little kid. My baby," Machado said.
Machado doesn't understand, and neither do thousands of other people, it seems.
More than 2,500 people have signed a petition on Change.org to revoke Deleon's bond called, "Justice for Diamond."
"Before and since his arrest the family of Diamond Alvarez has been receiving threats and has been harassed (sic) multiple times at their home and they now fear for their safety," the petition's page states. "Judge - Hazel B. Jones, granted Bond of $250,000.00 and the threat and tension has only gotten worse for the family, neighborhood and the City of Houston."
A public viewing for Alvarez will be held at Forest Lawn Cemetery on Almeda-Genoa Road today from 4 to 7 p.m.
Her funeral will be held on Friday.
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