Josepha Kasai (pictured) who firebombed an apartment building over a stolen iPhone was sentenced to 15 years in prison

A Virginia man who firebombed an apartment building over a stolen iPhone has been sentenced to 15 years in prison.

Josepha Kasai, 24, smashed a Molotov cocktail at the door of a third floor apartment unit in Alexandria, setting fire to the doorway and trapping nine individuals on the building's third floor in June 2016.

Molotov cocktails are incendiary devices that consist of a bottle filled with flammable liquid and with a means of ignition.

Court documents show Kasai then went outside and threw another Molotov cocktail at the third floor apartment unit, which broke through the bedroom window.

The entire building was evacuated due to the fire.

A victim inside the third floor apartment jumped from his balcony and Kasai chased the victim with what appeared to be a knife, according to the US Attorney's Office for the Eastern District of Virginia.

At the time, the victim told police that Kasai came to his door and dropped the Molotov cocktail, saying: 'I'm going to burn your house down and going to kill you.'

The victim, who knew Kasai, tried to get his mother and aunt to safety on the balcony, then jumped.

After Kasai's arrest, he informed law enforcement he intended to kill the victim who jumped from the balcony and claimed the victim had previously stolen his iPhone.

He reportedly told police that killing the victim would have made him 'proud'.

Kasai was convicted of arson and possession of an unregistered destructive device in October 2017.