Israel Hernandez-Llach had turned 18 shortly before police found him spray-painting a shuttered building early Tuesday.
The teen ran but was eventually cornered. Chief Ray Martinez says the teen ran at officers and one shot him with a Taser in the chest. Hernandez-Llach went into medical duress and died at a hospital.
His sister, Offir Hernandez, told The Miami Herald the family wants answers. They're seeking an independent investigation.
The medical examiner didn't rule on a cause of death after an autopsy yesterday. Further tests are pending, but the police chief says the teen didn't suffer from any other injuries.