A teenager who prosecutors say set a mattress fire that killed a New York City police officer and injured another officer has been found guilty of murder.

Eighteen-year-old Marcell Dockery also was convicted of arson and assault charges Thursday after a trial at Brooklyn Supreme Court.

New York Police Department officers Dennis Guerra and Rosa Rodriguez were trapped in the April 6, 2014 fire and overcome by smoke in the Brooklyn apartment building.

Guerra died three days later. Rodriguez spent six weeks in a hospital.

Dockery testified in his own defense, and said he discovered the fire and tried to save other residents.

In a note announcing the verdict, jurors wrote to the judge that Dockery “didn’t mean to harm anyone” and that they “hope leniency can be shown.”

(AP)