District Attorney Joe Khan announced the probe Monday, describing the two deaths as linked by circumstance. "They are enjoined by tragedy," Khan said.

The earlier case dates to the night of Aug. 12, when Ronald Davenport was walking through the parking lot of Grundy Hall, the county-owned senior residence where he lived with his wife, and was struck and run over by a Bucks County Transport bus.

According to Khan, the driver, 69-year-old Blair Vanacore, got out of the bus and approached Davenport, who was seriously injured and reportedly muttered, "call 911." Khan said Vanacore then "told the dispatcher that someone had fallen in the parking lot, gathered the victim's belongings and placed them next to him. Did not render aid, did not wait for police and left the scene."

Police identified Vanacore through his 911 call, and he later returned to the scene, authorities said. Khan said Vanacore gave investigators an interview and provided a blood sample that showed no drugs or alcohol in his system. Investigators have not determined why he failed to see Davenport.

Khan said Vanacore told investigators that "he'd run over a shoe," and allegedly explained that he left because "he believed he'd get in trouble with the company if he didn't return the bus to the depot that evening."

Vanacore is expected to turn himself in Tuesday to face charges including accidents involving death or injury and careless driving, Khan said. Attempts to reach him for comment were unsuccessful.

The second fatality occurred last week, when a Bucks County Transport bus struck and killed 67-year-old Katie Semisch in the parking lot of the Bucks County Free Library. Khan said that investigation remains ongoing, as does a separate review of the nonprofit's policies and procedures.

In a statement, Bucks County Transport said it is committed to providing safe and dependable transportation services and that, "As part of that commitment, BCT is reviewing safety policies and procedures to identify opportunities to further strengthen its operations."

Khan said his office intends to press for answers about how the deaths occurred and what safeguards the nonprofit has in place. "Somebody ought to be asking those questions, and we are going to be doing that work," he said.

The investigation adds scrutiny to a service that many older residents and people with disabilities rely on for medical appointments, errands and daily travel. Both deaths occurred in parking lots — settings where pedestrians and large vehicles share space with limited formal traffic controls — a detail that may figure in the broader policy review.