The accident happened around 11:00 Friday night near exit 39 in Old Westbury.
According to investigators, Officer Michael Califano, 44, was conducting a traffic stop at the time. Califano was sitting in his car with his lights blinking when a flatbed truck struck the cruiser from behind, authorities said.
The impact propelled the cruiser under a stopped box truck, while the flatbed mounted the police vehicle's roof. The severely injured officer was freed from the wreckage with heavy cutting tools, but died hours later at a hospital.
Califano had been on the force for 12 years.
Police identified the flatbed truck driver as 25-year-old John Kaley of New Britain Conn.
Kaley was arraigned in Hempstead District Court on charges of criminally negligent homicide, third-degree assault and failing to move over for an emergency vehicle, police said.
Three other people suffered less serious injuries in the wreck, Nassau County police Lt. Kevin Smith said. They included two people who were in the box truck and a female passenger in the flatbed truck. All were being treated at a hospital.
The LIE was closed in both directions while police investigated and crews cleared the accident scene.
The highway fully reopened just after 8:00 a.m.