Two Pennsylvania State Police troopers and a civilian were killed in a car crash on I-95 early Monday, in what law enforcement officials described as a possible DUI incident.

Colleagues and friends remembered the fallen officers as devoted public servants and young community leaders whose careers were cut short, with unanswered questions as the investigation continued into Monday evening.

The troopers responded to calls about a man walking in a southbound traffic lane near Lincoln Financial Field around 12:45 a.m. Monday. As they tried to bring the man into custody and out of harm’s way, a vehicle traveling at a high speed attempted to pass them in the shoulder lane, fatally striking both troopers and the civilian, according to state police.

Captain James B. Kemm, commanding officer for the state police in the Philadelphia region, said the force of the crash threw the troopers into the northbound lane. Police backup arrived to find witnesses performing CPR on the three victims, who were pronounced dead on the scene.

“Right now we are conducting an active investigation that is DUI-related,” Kemm said at a news conference.

Prosecutors have not yet decided on criminal charges, and the driver’s name was not released. District Attorney Larry Krasner said Monday he couldn’t discuss the details, noting only that a “young driver is potentially facing extremely serious consequences.”

State police identified the fallen officers as Trooper Martin F. Mack III, an 8-year veteran, and Trooper Branden T. Sisca, who joined the force last year.

Officials were withholding the name of the civilian until his family is notified, and declined to answer further questions on the investigation.

“Troopers Mack and Sisca made the ultimate sacrifice this morning while assisting a citizen in need,” said Colonel Robert Evanchick, commissioner of the Pennsylvania State Police. “They braved traffic along the busy interstate to assist a citizen whose own life was in danger. There’s no greater act of selflessness.”

Sisca and Mack were assigned to Troop K, which patrols state highways in Philadelphia and Montgomery and Delaware Counties.

Sisca, of Trappe in Montgomery County, came from family committed to public safety.

The 29-year-old officer was the son of Deputy Craig Sisca, a 10-year veteran of the Montgomery County Sheriff’s Office, according to Sheriff Sean Kilkenny. The younger Sisca graduated from the state trooper academy in 2021 and served as a volunteer fire chief with the Trappe Fire Company, where his wife, father, and father-in-law are also members.

He had married last fall and, according to an online baby registry, he and his wife were expecting their first child in July.

Standing with members of the Trappe Fire Company on Monday afternoon, Deputy Chief John Bolger called Sisca a visionary leader who took the helm of the volunteer engine in January.

“Even in that short period of time he brought our fire company forward with tremendous strides and introduced us to tremendous leadership initiatives that we are going to continue forward with. He was an example to all of us,” said Bolger.

About a dozen of Sisca’s friends attended the news conference, but were too overwhelmed with emotion to speak with reporters. Marcus Dolny, Trappe borough manager, called Sisca “a pillar” of the community who was still under the age of 30.

“You look for people like that. That’s your future, the building blocks for a community,” he said in an interview.

Chris Leder, 46, a former member of the fire company, said Sisca’s enthusiasm for public service was contagious: “He put 150% into everything he did.”

Mack, 33, was similarly dedicated to a life of service.

Known as “Marty” to his friends and family, he joined the state police in 2014, after stints as a private investigator and teacher-counselor at the Glen Mills schools, according to a Linkedin profile. On social media, he rooted for the Eagles and his local high school lacrosse team in Bristol Township, Bucks County, where he was also the member of Saint Mark Parish community.

“We know that Marty lived his life for the service of others,” Dr. John E. Cooke, president of Mack’s alma mater, Monsignor Bonner High School, wrote in a statement. “Our thoughts and prayers go out to the entire Mack family as well as all the families affected by this tragic incident.”

Dave Codell played amateur club rugby with Mack in the early 2010s, and recalled him as a consummate team player. He said Mack came to social events to support the local league — even when he wasn’t actively playing.

”He struck this incredible balance where he respected everyone’s time, but he was also really funny,” Codell said. “He would do the hard work. There were no half measures.”

Following the on-duty death of another state trooper in 2016, Mack wrote on Facebook that he and his colleagues in the Philadelphia region drove to the funeral in Altoona to “to lay one of our own to rest.”

Mack leaves behind a wife and two young children, according to social media. Family members have requested privacy.

State flags flew at half-mast in honor of the troopers as the crash probe carried into the evening.

Interstate traffic was shut down for hours as police investigated the crash site, where a state police SUV appeared with both driver-side doors ripped off. The hatchback that struck the officers and civilian sat parked nearby. Police said the driver remained at the scene after the crash.

Shortly after 6 a.m., Philadelphia police officers riding motorcycles led a procession to transport the bodies of the troopers from the scene.

At least 22 Pennsylvania troopers have died in automobile crashes in the last century, according to state police. The last fatality was in 2017, when a state police SUV collided with a garbage truck in Westmoreland County. A state trooper was injured in a crash that killed a Lower Merion firefighter on I-76 last year, after a driver struck a group of first responders who were tending to an accident scene.

Assistant District Attorney Joanne Pescatore, who leads the Philadelphia DA’s homicide unit, said prosecutors consider a variety of factors when deciding whether to file charges in a vehicular case, including whether a person was under the influence, speeding, or engaging in other forms of dangerous driving.

Gov. Tom Wolf said the crash marked a sad day for Pennsylvania.

“There are three families mourning the loss of loved ones,” Wolf said at a news conference. “It’s a reminder for the state troopers of what a heroic thing they do for us each and every day. For all three it’s a reminder of how precious and fragile life really is.”

Staff writer Anna Orso contributed to this report.