Sherria Daniel says her family has many questions about what caused her brother, Sean, 50, to die Tuesday while in police custody.
"Whatever [the] Yonkers Police Department did to him will come out," Daniel says.
Yonkers police say Sean died after he was rushed to a hospital when he became unresponsive after being placed in handcuffs.
Police say they cuffed him after two unsuccessful attempts to taser him, saying he was armed with a knife and attacked several people inside a Bruce Avenue apartment Tuesday night.
However, Daniel says her family didn't even know Sean had died until they received a call from an organ donation society.
"They're the ones that called my parents, my mom and my sister, and told them that something does not seem right and that they need to contact Saint Joseph Medical Center," Daniel says.
Daniel says the family immediately headed to the hospital, only to learn they were not allowed to see or identify Sean's body.
"What is Yonkers police covering?" Daniel asks.
Yonkers police say their Internal Affairs Division immediately opened an investigation. They say their findings, so far, show no indication that the taser deployment or any action taken by their officers caused Sean's death.
Police also say body-worn camera video revealed Sean was using drugs before the alleged attacks that police say seriously injured two people.
They add that an autopsy is underway, and an exam has identified underlying medical conditions that may have contributed to his death.
"What medical conditions? My brother was one of the healthiest and strongest people," Daniel says.
Daniel says her family is now lawyering up.
"They killed the wrong one because we're not being quiet about it. We're going to demand justice, and we're actually not going to stop," Daniel says.
The state attorney general's office is also looking into what happened, as required by law.