Hartford - A state judge told a former Windsor Locks police officer that he should have known better than to drink alcohol and drive before sentencing him to five years and four months in prison Monday for an off-duty car accident that killed a 15-year-old boy riding a bicycle two years ago.

The punishment handed down by Hartford Superior Court Judge Joan Alexander was part of a plea bargain between prosecutors and former Officer Michael Koistinen, 26, who pleaded no contest to second-degree manslaughter and evidence tampering in June.

Koistinen apologized in court to the family of Windsor Locks High School sophomore Henry Dang, who died after being thrown nearly 200 feet after being struck by Koistinen's car. Police said Koistinen had been drinking for several hours and was going more than 70 mph in a 35 mph zone when he hit Dang, who was riding home from a friend's house around midnight on Oct. 30, 2010.

"I'm extremely sorry, and I never meant this to happen," said Koistinen, who wore a black suit and white shirt with a black tie.

Koistinen's lawyer, Raymond Hassett, called the case "an epic confluence of disastrous circumstances." Hassett said Koistinen is a soft-spoken, compassionate young man who will live with his guilt forever.

But Dang's family, in a statement read in court by prosecutor John Fahey, scolded Koistinen for his "stupidity" and called his actions "selfish and cold-hearted." The family said Koistinen did not deserve their forgiveness.

"Michael took something precious and priceless from us," the family's statement said. "Our lives will never be the same."

Dang's family described him as a respectful boy who was loved by his family and friends and never lied or stole. They said he took a job delivering newspapers when he was 13 to make money instead of asking relatives for cash.

The family also put together a slide show of photos of Dang that was shown in court on a screen right next to where Koistinen was sitting.

Nearly 20 family, friends and former co-workers of Koistinen attended the sentencing. About a half-dozen members of Dang's family, seven of his friends from school and all the friends' mothers also were there. Several people cried quietly during the proceeding. Some of the mothers said outside the courtroom that Koistinen's prison sentence isn't long enough.

Koistinen was led out of the courtroom by marshals to begin serving his sentence. He also must serve five years of probation and perform 100 hours of community service after his prison term. During the probation, he will be banned from using alcohol and illegal drugs and will be subject to random urine testing.

Alexander said Koistinen knew the potential dangers of drunken driving because he was a police officer. The judge said Dang's family requested that Koistinen speak about those dangers during his community service, and Hassett said Koistinen would do so.

Both Koistinen and his father, former Windsor Locks police Sgt. Robert Koistinen, were fired because of the accident. Robert Koistinen was also arrested and awaits trial on a charge of hindering the investigation.

Police said Michael Koistinen drank beer and other alcoholic beverages for several hours, including outside a University of Connecticut football game and at a Suffield bar, before the accident. One of the Windsor Locks officers who responded to the crash scene was his father.

A state police investigation found that Robert Koistinen drove his son away from the crash site to the police station and back as many as three times, and later prevented an investigating officer from interviewing and getting a blood sample from Michael Koistinen while he was being treated at a hospital.

An independent investigation found a series of problems with the way police responded to the accident, including officials' failure to question Michael Koistinen at the scene about possible alcohol consumption and their failure to test his blood-alcohol level. The report found no evidence of a cover-up, but faulted department officials for a lack of leadership and poor management.

Because a blood test wasn't done, authorities said they couldn't charge Koistinen with drunken driving. Court records show that hospital officials destroyed a urine sample from Koistinen under hospital policy before police obtained a search warrant for Koistinen's medical records.

Last year, Dang's family settled a wrongful death suit against Michael Koistinen and a former tavern owner for $420,000.