A New York police officer who shot dead an unarmed teenager who was inside his own home has been indicted on manslaughter charges, reports say.

Ramarley Graham was killed as he fled to the bathroom of his grandmother's residence in the Bronx on February 2, prompting a wave of protest over the perceived excessive use of force.

The gunman, 30-year-old NYPD officer Richard Haste, is said to have believed the the 18-year-old was armed. Graham was attempting to empty a bag of marijuana down the toilet at the time of the incident.

On Monday the New York Post reported that a grand jury in the Bronx returned first and second-degree manslaughter indictments against Haste in relation to the shooting. WNYC and NBC New York also carried similar reports.

A spokesman for the Bronx district attorney's office refused to comment on the case, other than to say that the leaked information had not come from them.

Likewise Jeffrey Emdin, a lawyer for Graham's family, said he had only heard about the charges secondhand. He added that no statement would be given before Wednesday, when the indictment is expected to be unsealed.

The incident occurred while police were staking out a local bodega thought to have been used as a front for selling drugs.

Officers observed Graham leave the store acting suspiciously, they said, leading them to believe he was armed.

After identifying themselves as police, the teenager ran to his nearby family home. Officers, including Haste, gave chase and cornered him in the bathroom of the second-floor apartment.

Haste is said to have yelled "gun, gun" before opening fire on the unarmed teenager. The teen was taken to Montefiore Medical Center where he was pronounced dead, the result of a single bullet wound to the chest.

It later emerged that Haste had not received the training required to work in the special unit to which he had been assigned.

In the aftermath of the shooting, the officer was stripped of his gun and put on modified duty. It has been reported that he will turn himself in to authorities on Wednesday, shortly ahead of the indictment being unsealed.

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