A Brooklyn teenager was sentenced to 19 years to life in prison yesterday for setting fire to a mattress in a hall of his apartment building, leading to the death of a responding police officer. Marcell Dockery, now 18, was convicted last month of murder, assault and arson after a two-week trial.

The fire in Dockery's Coney Island apartment building claimed the life of Officer Dennis Guerra and severely damaged the lungs of his partner, Officer Rosa Rodriguez. The saddest thing about the situation, according to Judge Danny Chun, speaking before laying down the sentence, was that they responded "because of their love for the job and their love for helping people in trouble, and because of that, Officer Guerra is dead."

In a statement taped by detectives the day after the fatal blaze, Dockery explained that he had returned to his Surf Avenue building from playing basketball on that fateful Sunday in April 2014 and was trying to get a key to his 12th floor apartment from his cousins, who lived upstairs. There was a mattress lying in the hallway, and when he got no answer, he said:

I got bored, so I walked down, and I started burning the edge of the mattress. I wasn't doing it to do anything wrong or nothing. I was just bored. When I set it on fire I could have sworn I blew it out...[The fire] wasn't big or nothing. So I started walking back down the hallway...But then I turned back around and the whole hallway started getting mad smoky and I started seeing the whole mattress still on fire.

At that point, he recounted, he rushed up and down the hallway, knocking on doors and alerting neighbors that there was a fire. By the time Guerra and Rodriguez responded, the fire was raging, and the elevator they took to the 13th floor opened on a wall of black smoke. They were overcome by the smoke, and though firefighters rescued them, Guerra died of his injuries. Rodriguez will need a lung transplant, according to the New York Post.

The fatality prompted the NYPD to clarify its guidelines for officers responding to fires, and to forbid them from taking the elevator when doing so.

NYPD Officer Rosa Rodriguez being released from the hospital a month and a half after responding to the Coney Island apartment building blaze that left her burned and her lungs severely damaged. (Spencer Platt/Getty)

In a victim impact statement, Guerra's widow Cathy said, "The family acknowledges that when Marcell Dockery set fire to the mattress he didn't mean to hurt anyone that day — but others suffered by his actions."

In rendering their verdict, jurors expressed a similar sentiment, writing, "We would like to express our sincerest feeling that the defendant didn’t mean to harm anyone as a result of his actions. While sentencing did not play a role in our decisions, we hope leniency can be shown."

At trial, Dockery claimed that his confession was coerced and that he is innocent.

Prosecutors had asked for a sentence of 18 years to life, citing Dockery's admitted fascination with fire predating the tragic 2014 blaze.

"A senseless act of arson cost a very courageous police officer his life and destroyed the health and career of another heroic officer," Brooklyn District Attorney Ken Thompson said in a statement. "The sentence imposed by the court today reflects the severity of the crime committed by the defendant."

Prosecutor Howard Jackson said he was "bothered and disturbed" that the teen recanted his confession.

Dockery's lawyer, Jesse Young, told the judge, "He is innocent and will appeal."