A New Jersey State trooper was responding to reports of an erratic driver Monday evening when that driver's Toyota Corolla veered off the southbound lanes of Route 55, crossed the grassy median, entered the northbound lanes, and crashed head-on into Frankie Williams' patrol car, authorities said.

Williams, 31, who had graduated from the academy in January and was working on his master's degree in criminal justice, was flown to Cooper University Hospital, where he later died. He is the fourth state trooper to die in a car accident in less than two years.

In its 95-year history, the New Jersey State Police has never lost so many troopers to motor-vehicle crashes in such a short period.

Lloyd Rudley, 61, of Elmer, N.J., who drove the Corolla that police said struck Williams' car about 7 p.m. Monday, was pronounced dead at the scene.

Several witnesses reported a vehicle driving erratically in the area, and state police said those reports matched the description of Rudley's car. Authorities said on Tuesday they were still investigating what caused Rudley to drive into oncoming traffic.

Rudley, a former physician, worked in a private practice at the Institute of Pennsylvania Hospital, which closed in 1997, according to Penn Medicine officials. More recently, public records indicate he had a practice in Elmer, but the phone number there did not work Tuesday, and his family could not be reached.

Col. Rick Fuentes, superintendent of the state police, called Williams' death "a terrible loss."

"Trooper Frankie Williams was one of our best and brightest young troopers," he said in a statement Tuesday. "His tragic death has left the entire State Police family heartbroken."

Fuentes said Williams was married.

Williams, who was assigned to the Port Norris station, had earned respect from his peers, "establishing himself very early in his career as an outstanding trooper able to think quickly on his feet and make sound decisions," the state police said on its Facebook page Tuesday.

In August, Williams drew praise when he broke the window of a locked car with a baton and rescued a dog suffering from heat stroke. He then poured water on the dog in the shade, authorities said.

"He performed his duty more like a six-year veteran than a 6-month rookie," the state police said on Facebook.

The agency was already reeling from the loss of three troopers in recent years before Williams' death.

Trooper Anthony Raspa, 24, died in May 2015 when his car struck a deer in Monmouth County.

Trooper Eli McCarson, 30, died in December 2015 when his car crashed into a utility pole in Salem County.

Trooper Sean Cullen, 31, was fatally struck by a car in March while assisting at the scene of a vehicle fire on I-295 in Deptford Township, Gloucester County.

Williams graduated from Rutgers-Camden with a bachelor's degree in criminal justice in 2012. He was recently working on his master's degree.

"He was just a very outgoing, friendly, and really charming guy, very likeable," said Professor Jane Siegel, chair of the Rutgers-Camden criminal justice department. "He will certainly be missed here."

On Williams' LinkedIn page, many users commended him for his customer service, public speaking, and leadership. He said in his LinkedIn bio he was interested in cyber-security.

"As a graduate student at Rutgers University, my research is predicated upon creating awareness for cyber-crime and contributing to public awareness," his bio said, "in an effort to minimize cyber-crime victimization."

Williams, before joining the state police academy, worked at the Lowe's along East Black Horse Pike in Egg Harbor Township from 2008 to 2015. He started as a customer service associate and rose to the position of loss prevention manager. Grief counselors were called there Tuesday.

"Those who worked with him remember his infectious smile and the impression he left when you met him," said Karen Cobb, a Lowe's spokeswoman. "He shared with co-workers that his dream was to get his master's degree and become a state trooper. We are saddened by his loss, but are comforted that he lived his dream, if only for a short while."

On Tuesday afternoon, people walked in and out of Williams' Egg Harbor Township home, where several cars and a state police cruiser were parked out front. The state police said the family had requested privacy.

Alicia Ruiz, 38, who lives nearby and said she knows the family through a mutual friend from church, said she visited Williams' home Tuesday to bring a cake and offer condolences.

"I feel very sorry for his family, what they are going through," she said.

Eleven people, including Williams and Rudley, have died in accidents on Route 55 this year, according to state police data. Last year, seven people were killed on the state highway, which stretches 40 miles through Gloucester, Cumberland and Salem counties. In some cases, vehicles slid off the roadway due to weather conditions or other circumstances.

Public officials in New Jersey and police departmens and organizations from around the region and country were mourning Williams' death.