"They took the life of a young man, just reckless and senseless acts of abuse of power, and for nothing, for nothing. My son can't tell his story; so we have to tell it for him," said Mendoza's dad, John Mendoza Sr.
His family said the story started with Mendoza coming home from Texas State University for the summer.
They said he was driving home with friends when a Brazoria County sheriff's deputy attempted to pull him over in Lake Jackson last Monday morning.
Surveillance video captured the short pursuit after deputies said Mendoza didn't stop.
His family said it ended in Mendoza's garage when a deputy shot and killed him inside his car. His family said Mendoza was not armed.
"My nephew was murdered in cold blood; that's exactly what that was," said Glenda Mendoza, Mendoza's aunt.
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The district attorney's office and Texas Rangers are leading the investigation and confirmed earlier this week that the case will be sent to a grand jury. The Mendoza family and the community are asking for more, including for the Department of Justice to investigate.
"Let's do what's right; let's get transparency done because it's the right thing to do," Mendoza Sr. said.
"I want the District Attorney Tom Selleck to present the grand jury a murder indictment," said Mendoza's aunt, Glenda.
Mendoza's dad and aunt are now remembering the football player, dean's list student and friend, whose life was cut short.
"He was my heart; he was just such a great young man," Mendoza Sr. said.
"I want to say, 'I love you. I'm so proud of you; you're a very good boy. You will never be forgotten, and I'm here for you. And I'm going to fight till the end. I love you, John,'" said Mendoza's aunt, Glenda.
It's still not clear what the initial traffic stop was for.