"Please come forward, we want to know what happened," said Chapa's sister, Melina Gonzalez.
The family has requested bodycam video, Chapa's autopsy report and the police report, but say Alvin police won't give it to them.
"The complete secrecy in this situation is horrible, but it speaks volumes something wrong happened and it was the Alvin Police Department that did something wrong," said the family's attorney, Randall Kallinen.
Chapa's father, Isaac Chapa, said, "What we're looking for is clarity and understanding. We want to understand why my son was fatally shot."
The family also says police raided their home.
Police tell ABC13 officers did give repeated commands for Chapa to drop a weapon and that after getting him on the ground, police say he brought that weapon back up as officers moved in on him. That's when they say an officer shot him, ultimately killing him.
"If there was wrongdoing on my son's part, I want to know what it was. I want to know what actually happened. We're hearing so many different stories which one is the truth? That's what we want to know," said Chapa.
Alvin Police responded to the lawsuit with the following statement:
"On July 15, 2018, Alvin police officers were involved in a deadly shooting with a suspect who was armed with a handgun. Immediately prior to the deadly encounter, the suspect discharged the handgun during a disturbance at his family's home at which time the family called 911.
The incident was fully investigated by the Alvin Police Department, Brazoria County Sheriff's office, the Brazoria County District Attorney's office, and the Texas Rangers. The investigation was referred to the Brazoria County grand jury and the involved officers were cleared. The City of Alvin and the Alvin Police Department have fully cooperated with every aspect of the incident since it occurred.
Upon receiving notice of pending litigation by the family, the City of Alvin has released information and records in compliance with the law and consistent with established standards when litigation is pending."
VIDEO: Aftermath of deadly police involved shooting
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