Critics of Sheriff Joe Arpaio gathered outside the 4th Avenue jail Tuesday afternoon to protest the death of an inmate at that facility.
40-year-old Raymond Farinas died 11 hours after he was booked on weapons charges on June 3.
According to the sheriff's office, the medical examiner says it appears he died of natural causes.
The Jail Crimes Unit says it appears he did not suffer any injuries at the hands of fellow inmates or detention officers.
While an official cause has yet to be determined, the man's family feels he met with foul play.
Activists are calling on the FBI to conduct an investigation.
"If somebody died at my job or if I killed someone at my job or if I was under investigation for someone dying under my watch, you think I'd be free to walk around or it would be public news? It wouldn't be hidden," said protester Eric Rodriguez.
"There doesn't seem to be any end to it and we just need the awareness, we need people to wake up and come out and you know be heard," said protester Gail Shoultes.
Farinas is the second inmate to die at the 4th avenue jail in the past six months.
In December, Marty Atencio died after he was restrained and shot with taser guns when he became combative.
The medical examiner ruled the army veteran suffered complications from cardiac arrest.
Last Friday -- his family filed a $20 million notice of claim against the Maricopa County Sheriff's Office and Phoenix Police, which is the first step toward filing a lawsuit.