NEW YORK (AP) — A white police office's chokehold on a black New York City man last month caused his death, the medical examiner announced Friday, ruling it a homicide.

The officer used the chokehold on Eric Garner during his arrest last month for selling untaxed, loose cigarettes

Garner, 43, was killed by "the compression of his chest and prone positioning during physical restraint by police," said medical examiner spokeswoman Julie Bolcer. Asthma, heart disease and obesity were contributing factors, she said.

Garner's videotaped confrontation with police has caused widespread outcry and calls by Rev. Al Sharpton, a prominent civil rights activist, for federal prosecution. Sharpton believes chokeholds are used disproportionately on minorities.

Chokeholds are prohibited by the New York Police Department. The case is being investigated by local prosecutors who are awaiting a full autopsy report and death certificate from the medical examiner. The district attorney overseeing the case will have to determine whether to empanel a grand jury and charge officers in the death of Garner.

Garner's death has raised criticism of the broken windows theory of policing, a tactic championed by Police Commissioner William Bratton that posits that cracking down on relatively minor, low-level offenses such as selling loose cigarettes helps suppress more serious crimes. Officials have defended the policing tactic despite calls for it to be discontinued.

After the medical examiner announced its ruling, New York Mayor Bill de Blasio issued a statement Friday in which he extended his "deepest sympathy" to Garner's family.

The NYPD didn't immediately respond to a request for comment on the medical examiner's ruling. The officer who put Garner in the chokehold was stripped of his gun and badge pending the investigation, and another was placed on desk duty. Two paramedics and two Emergency Medical Technicians were suspended without pay.

Bratton has said the officer appeared to have placed Garner in a chokehold and has ordered a top-to-bottom redesigning of use-of-force training in the NYPD.