The vehicles collided near Exit 35 just after 4:45 a.m.
Several people were injured, although the extent of their injuries was not known.
The officer, identified as Joseph Olivieri, responded to the crash and was killed shortly after arriving when he was hit by another car that struck one of the vehicles involved in the initial crash.
James Ryan, 25, of Oakdale struck a 2008 BMW while driving his Toyota Camry.
Police say that he left the scene of the initial accident and continued eastbound on the Expressway. Ryan apparently stopped abruptly in the left lane, parallel to exit 35, and was struck by a 2005 Honda Civic.
The Honda came to rest in the right lane facing westbound. Ryans' vehicle came to rest perpendicular to the center median.
Officer Olivieri positioned his marked patrol car in the right lane in front of the Honda. The officer exited his vehicle, crossed to the HOV lane to render assistance when he and the Toyota were struck by a 2002 Cadillac Escalade.
Olivieri was transported to North Shore University Hospital in Manhasset, where he was pronounced dead at 5:25 a.m.
Ryan is being charged with second-degree vehicular manslaughter, second-degree reckless endangerment, criminal possession of a controlled substance, reckless driving, driving while intoxicated and leaving an incident without a report.
He will be arraigned on Friday at First District Court in Hempstead.
Olivieri was a 19-year police veteran, having spent five years with the NYPD before joining the Nassau County Police Department in 1998. He was with the Highway Patrol since 2005.
He is survived by his two children, 21-year-old Amanda and 18-year-old Daniel.
This is the second member of Nassau's Highway Patrol killed in the line of duty on the LIE in less than two years. Officer Michael Califano died in February of 2011, just a few miles east of this scene, when his car was hit from behind as he sat inside, writing a ticket. He is the 33rd officer to die in the line of duty in the department's history.
District Attorney Kathleen Rice issued the following statement:
"Early this morning, one of our brave police officers was killed in the line of duty. I'm deeply saddened by our community's loss and my heart breaks for the officer's family, friends and colleagues. What I can promise is that we will get to the bottom of exactly what happened this morning, and that we will continue to work tirelessly every day to protect those who risk their lives for the safety of our communities."
Flags will fly at half staff for the next 30 days.
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