August 15, 2008 - 7:10 AM

A Hopkinton police officer was killed early yesterday when a car rear-ended his 2004 Harley-Davidson motorcycle on Route 202/9 in Henniker. He was driving home from work.

Sean Powers, 24, of Hillsboro, an Iraq War veteran who joined the Hopkinton department in April, was pronounced dead on the scene. He was hit shortly before 1:30 a.m. by a 1992 BMW sedan driven by 22-year-old Jeffrey Dennis of Gould Pond Road in Henniker. Dennis may have been drunk at the time of the accident, the police said.

Dennis and a friend who was riding in his car fled the scene on foot after Powers was hit by a second vehicle that had been following the BMW. All three vehicles were traveling westbound, according to the police.

Dennis called his parents by cell phone several hours after the accident. They had already been woken up by the police, said his mother, Susan Dennis. She and her husband got in their car, and reached their son about a half mile from the accident on Old West Hopkinton Road.

"We just wanted him to be brought in safely," Susan Dennis said.

Dennis was arraigned yesterday at the Concord District Court on four charges: aggravated driving while intoxicated; two counts of negligent homicide; and conduct after an accident. Judge Gerard Boyle ordered him held on $500,000 cash bail.

The two negligent homicide charges represent alternate theories, said Merrimack County Prosecutor Dan St. Hilaire. If Dennis is found guilty of driving under the influence of alcohol then the state will argue that he was guilty of Class A negligent homicide, which carries a prison sentence of up to 15 years. If the drunk-driving charge is dismissed, the state will argue for Class B negligent homicide, which carries a lesser sentence.

Officers from at least seven law enforcement departments participated in the search and preliminary investigation yesterday. Two scent-sniffing dogs, a state police helicopter and other specialty teams, including the state Technical Accident Reconstruction team that uses lasers to analyze and reconstruct an accident, were on the scene, said St. Hilaire.

"We really appreciate the fact that the other agencies were there, because we needed them," said Henniker Police Chief Tim Russell.

Russell said he was among the officers who took Dennis into custody at around 9 a.m.

"He looked like he was pretty scared," Russell said.

The driver of the second vehicle - a 2000 Honda Civic - that hit Powers remained on the scene and gave a statement to the police. That driver does not face charges related to the incident.

Powers, who served two tours of duty as a Marine in Iraq, was wearing a helmet, Russell said.

"The town was looking forward to a long relationship with him," the Hopkinton Selectmen wrote in a statement. "Officer Powers's death was tragic and needless. We will all miss him."