The trial began Friday for the man accused of setting a fire that resulted in the death of an NYPD officer.

Marcell Dockery is charged with second-degree murder, assault and arson for allegedly setting a mattress on fire inside a Coney Island apartment building in April 2014, which led to the death of Officer Dennis Guerra.

Both sides were asked to present opening statements in court, but only the prosecutor did so. Defense attorney Jesse Young opted not to give a statement.

In his opening statement, Assistant District Attorney Howard Jackson said Dockery, who was 16 years old at the time, should have known better than to light the fire. Jackson added that Dockery had gotten into trouble before for lighting fires.

Jackson said Dockery confessed to setting the fire, giving police a detailed account of how he saw the mattress in the hallway of the 13th floor and decided to light it, claiming he was bored.

When Officer Guerra and his partner Officer Rosa Rodriguez arrived at the scene, the fire had already engulfed the entire floor.

Guerra eventually died in the hospital from the smoke and flames.

The prosecution began calling witnesses to the stand to describe what happened on the day of the incident.

Prosecutors plan to call up Officer Rodriguez, who they say is now on desk duty because her injures have left her unable to speak or breathe properly.

If convicted, Dockery faces up to 25 years to life in prison.