An upstate New York man tragically killed his own sister when he “abruptly” veered into oncoming traffic before fatally crashing into her vehicle, cops said.

Dahlia Klink, 24, and two minors were killed in the crash after the 2005 Ford Focus they were in smacked head-on with the 2006 Dodge Ram operated by her brother, 21-year-old Evan Klink, according to state authorities.

Molly Kibler, only 6, and 17-year-old Havanah Lopez were pronounced dead at the scene on Freedom Road in the town of Freedom Saturday afternoon. Dahlia Klink succumbed to her injuries at Erie County Medical Center Sunday.

A 4-year-old passenger in the Ford was also rushed to the hospital with serious injuries following the crash.

Meanwhile, driver Evan Klink was treated for injuries and taken to the state police station in Warsaw, state police said.

A passenger in the Dodge, 19-year-old Cameron Klink, was taken by helicopter to a hospital with serious injuries.

State investigators are still piecing together how the crash unfolded, but witnesses told police that the Dodge pick-up truck “abruptly” went into the oncoming lane though it’s still unknown if he made the sudden maneuver on purpose, a state police spokesperson told The Post Monday.

The rate of speed Evan Klink was going is also under investigation as the state police’s collision reconstruction unit reviews physical evidence from Evan Klink’s vehicle, the spokesperson said.

State police are working with the Cattaraugus County District Attorney’s Office to obtain a subpoena for the driver’s blood from the hospital where he sought medical attention, according to the spokesperson.

Authorities have not yet said if any of the passengers in either vehicle were related to the drivers.

The small town that has a population of less than 3,000 were in shock and grieving over the fiery crash.

“When I heard it was brother and sister — that hit. I couldn’t believe it,” Freedom resident Sue Fish told WKBW.

“How’s the driver of the truck going to live with himself now and the rest of the family?”

The speed limit on the stretch of road where the crash happened is reportedly 55 mph.

Three online fundraisers are raising money for funeral costs for Kibler, Lopez and Dahlia Klink, who was remembered as an “amazing mother to her 2 beautiful daughters” on the GoFundMe page.

The small town where the crash happened is located in Cattaraugus County and is about 50 miles from Buffalo.