Is This A Legitimate Criminal Charge?

On Long Island, New York, a police investigating an accident is hit and killed while he was investigating a traffic accident and the person who hit the officer is not charged- the guy who the officer was assisting was charged in the officer's death.
From Newsday: An accused drunken driver -- charged with vehicular manslaughter after a different vehicle struck and killed the Nassau County police officer who came to his rescue -- is free on bond.
The driver, James Ryan, 25, of Oakdale, expressed sympathy Friday to the family of Officer Joseph Olivieri, who died on the Long Island Expressway in the pre-dawn hours of Thursday morning.....
Ryan made the comments to reporters as he was being led from police headquarters to his arraignment ....
 The events leading up to Olivieri's death began with a call of a flat tire on the expressway at about 4:45 a.m.
Instead of a flat tire, it was an accident on the eastbound LIE that Olivieri came upon.
Police said in the minutes before the officer arrived, Ryan had collided with a 2008 BMW, then continued east and stopped abruptly in the left lane near Exit 35.
His car was struck by an oncoming 2005 Honda Civic, police said.
Olivieri then arrived and parked his cruiser in the right travel lane and crossed in the dark to help Ryan from his Toyota Camry. The cruiser's emergency lights were flashing, police said, as Olivieri crossed the expressway.
At about the same time, the driver of a Ford Explorer saw the accident and stopped before reaching the crash site.
The officer was hit by a 2002 Cadillac Escalade as he was assisting Ryan, police said.
Investigators believe the Escalade driver, who is not expected to be charged, saw the flashing lights of Olivieri's cruiser but didn't see Ryan's Camry "until the last minute." The driver swerved to avoid Ryan's car but struck Olivieri and the Camry, police said.
Friday. Ryan's attorney, Brian Davis of Garden City, said Friday before the arraignment that his client is being overcharged. Davis said prosecutors are stretching to link Ryan's actions to the sequence of events that caused Olivieri's death.  http://www.newsday.com/long-island/nassau/man-charged-in-officer-s-death-i-feel-bad-1.4132112
So, the officer is helping out the driver involved in the accident, who apparently is drunk, though barely and the officer is hit and killed by another driver and that driver is not charged at all.
I just don't think this charge will stand up, only because it sets a terrible precedent.  If an emergency worker is killed while assisting another person, drunk or not, and they are killed by a third party, then that means the person the first responder is helping can be charged criminally for the first responder's death, and that just doesn't seem right.
RIP to the officer and prayers to the family, department and the officer's friends, but in this case, it seems like the cops and prosecutor have over charged in this case, especially since the person who hit the cop was never charged.