An unlicensed cosmetologist from New York City was convicted Thursday of criminally negligent homicide for injecting silicon in the buttocks of a 43-year-old woman causing her death.

The convict, Elsa Then, 58, faces up to four years in prison. She was released on $10,000 bail until her sentencing Dec 12.

Then injected silicone to the buttocks and thighs of Fiordaliza Pichardo on March 16, 2009, according to the New York Daily News.

The silicone traveled through the bloodstream to her lungs and Pichardo died of a silicone embolism in her lungs two days later, according to the New York Times.

Silicone embolism is a rare but deadly side effect of the direct injection of silicone.