The early morning hours of Oct. 31, 2013, were a time of joy across Massachusetts, as Red Sox Nation celebrated its team's third World Series victory in 10 years.

It was less celebratory for State Police Sgt. Mark Lynch, now the head of the State Police union, who totaled his cruiser while off-duty that night.

Shortly after 1 a.m., Lynch drove his unmarked police car onto the median of Route 3 in Billerica, where it rolled over and came to rest on its roof, according to internal affairs records obtained by MassLive.

An internal investigation found he had violated department rules for using police cruisers while off the clock.

But he was not cited for the crash itself. Lynch told State Police Sgt. Shawn O'Neil, who responded to the scene, that a dark minivan had run him off the road -- a claim that O'Neil took at face value, according to the report he filed on the incident.

"The investigation reveals that Vehicle #1 was traveling in the left lane on Route 3 South, when a dark colored minivan forced vehicle #1 out of his travel lane and into the grass median. Vehicle #1 then rolled over and came to a final rest upside down in the median," O'Neil wrote. "At this time, Sgt. Lynch was unable to provide any further description of the second vehicle other than a dark colored minivan."

O'Neil's report does not describe any investigative measures other than taking Lynch's statement and his observations of skid marks in the grass median.

No other witnesses were present, O'Neil wrote. The report gives no indication that O'Neil searched for the vehicle that had allegedly caused a dangerous accident for one of his colleagues.

When asked about the crash during a brief phone conversation, O'Neil said "I don't know what you're talking about" and declined to comment.

An attorney with the State Police public records division confirmed there was no further investigation of the incident, beyond the crash and internal investigation reports reviewed by MassLive.

The cursory nature of the investigation is strange, Northeastern University School of Law Professor Daniel Medwed said in an interview -- particularly given the late hour of the crash and Lynch's statement that another vehicle ran him off the road.

"It's bizarre that there wasn't at least a field sobriety test or some additional steps," Medwed said. "It's doubly bizarre given the claim of a rogue menacing driver endangering a Sate Police officer. It's almost inconceivable to me that if the investigating officer credited that account he would not pursue it, both as a matter of protecting the state police and protecting public safety."

Lynch and the State Police Association of Massachusetts declined to answer questions about the circumstances of the crash or comment for this story.

In a statement, State Police spokesman David Procopio wrote that further investigation of the crash was not possible due to the limited description of the minivan. And he noted that the responding officer would have needed to have reasonable suspicion based on his observations of Lynch's condition to conduct any field sobriety tests.

"The crash was investigated as we would any other single-car rollover with minor injuries and no witnesses. The Sergeant who investigated the crash collected as much information as possible, and determined, based on his observations, that he did not have reason to pursue further investigative actions," Procopio wrote. "Sgt Lynch was subject to an internal investigation for using a department vehicle well after the conclusion of his shift. The charge was sustained and commensurate action was taken against him."

There are also inconsistencies between O'Neil's report that night and subsequent reports filed by Lynch and O'Neil over a week after the crash. In the initial report, O'Neil indicated that Lynch had been injured and had declined medical treatment at the scene.

But both Lynch's hand-written crash report, dated Nov.11, 2013, and O'Neil's full report filed Nov. 20 claim that Lynch suffered no injuries.

The claim that Lynch was uninjured also conflicts with the Billerica Fire Department's report on the crash. In an interview, Billerica Fire Chief Robert Cole said Fire Capt. Frederick Wiggins responded to the crash and found that Lynch had sustained a minor laceration.

Wiggins recommended that Lynch be checked out by ambulance EMTs, but he declined. The captain gave Lynch a bandage and ice pack, Cole said.

Wiggins, who is now retired, told MassLive he has no specific recollections about responding to the crash.

The Billerica Police Department told MassLive a police cruiser arrived at the scene, but departed after it became clear that State Police had already responded.

In December of 2013, about two months after the crash, State Police Major Francis Hughes ordered Lt. Richard Hunter to conduct an internal investigation.

The scope of the inquiry was limited. Hunter wrote that after reviewing reports and conducting interviews with O'Neil, Lynch and Lynch's unit commander, there was just one matter to investigate: whether Lynch was off-duty while he was driving the cruiser at the time of the crash.

Hunter's report does not address the circumstances of the crash or whether Lynch was at fault.

During Lynch's interview, Hunter asked him whether he was on duty at the time of the crash. Lynch referred Hunter to his written statement. Parts of that statement were redacted for privacy and investigative reasons when provided to MassLive.

"Upon completion of my assigned duties, I [redacted] for dinner and personal reasons," Lynch wrote. "At approximately 0104 hours on Oct. 31, 2013, I was traveling Route 3 southbound in Billerica."

Hunter concluded that Lynch was off-duty at the time, noting that his tour of duty had ended at 5 p.m. Lynch was found to be in violation of department vehicle use policy.

News of Lynch's 2013 crash, which has not been previously reported, comes as the union he leads finds itself increasingly entangled by the series of scandals afflicting the Massachusetts State Police.

Lynch was appointed President of the State Police Association of Massachusetts on Oct. 1 to serve out the remainder of former President Dana Pullman's term.

Pullman, a 31-year veteran of the state police, resigned as union president in late September, citing personal reasons. But the Boston Globe has reported that at the time of Pullman's resignation, federal authorities had begun an investigation of union political donations and of a charitable trust run by Pullman's wife.

And on the day of Pullman's resignation, State Police Col. Kerry Gilpin sent the union a letter saying the department would begin cracking down on allegedly improper uses of publicly funded union business leave.

Per the union's contract with the State Police, SPAM can allocate 10,000 hours per year of paid leave for union representatives to attend disciplinary hearings, union board meetings and other union functions.

The union has strongly disputed her conclusions, filing a labor complaint and lawsuit claiming that the department unfairly changed leave policies without negotiations, the Boston Globe reported.