Then- Westampton Township Police Officer Sean Cullen works with K-9 Robi during a demonstration at Westampton Township Police Department's National Night Out. Cullen died on March 8 while serving as an NJ State Trooper. (Nancy Rokos / Burlington County Times)

A New Jersey State Police trooper has died from injuries after being hit on Route 295 in Deptford Monday night.

State Police said Trooper Sean Cullen, 31 was on duty, responding to a car fire and crash as he walked along the highway and was struck by a passing car driven by a 22-year-old woman.

Authorities said the woman immediately stopped and cooperated with State Police. She has not been charged with any crime and was cooperating with the investigation.

Cullen was flown to flown to Cooper University Medical for treatment of severe head injuries.

"His family members and numerous troopers and law enforcement personnel from several different agencies held vigil late into the night at the hospital," State Police wrote in an announcement of his death early Tuesday morning. "Doctors pronounced him deceased shortly after 12:30 a.m. Colonel Rick Fuentes broke the news to those gathered in a waiting room."

Cullen was engaged to be married and had a 9-month-old son. He is also survived by his parents, two brothers and one sister.

He was born in Dublin, and his family immigrated to the United States when he was 3.

He was a 2003 graduate of Cinnaminson High School, where he was a standout wrestler. He was an All-American wrestler at Lycoming College in Pennsylvania, where he earned a degree in criminal justice.

Gov. Chris Christie on Tuesday offered his condolences to Cullen's loved ones.

"Every day, the men and women of the New Jersey State Police put their lives on the line to protect our citizens," Christie said in a prepared statement. "The sudden and tragic loss of New Jersey State Trooper Sean Cullen reminds us how fragile life truly is and the dangers police officers face daily on the job."

Cullen was a member of the 154th State Police Class. State Police said he was stationed at Bellmawr Station and had been a trooper for about two years.

The last New Jersey state trooper to die in the line of duty was Eli McCarson. He was responding to a call in Salem County on Dec. 17 when his patrol car struck a utility pole.

McCarson, 30, was trapped while rescuers in Quinton Township opened the jammed doors, and he died a short time later at a hospital.

The Associated Press contributed to this report.