A Victorian driver has been charged over a fatal crash as detectives investigate another three-car collision near the Victoria-NSW border.
Detectives on Saturday charged a 25-year-old Shepparton man with culpable driving causing death after the car he was driving crashed in Arcadia on April 3.
The man's passenger, a 19-year-old Shepparton woman, died at the scene.
The man has been remanded to appear in Shepparton Magistrates Court on August 23.
Meanwhile, detectives are investigating Friday night's fatal three-car collision near the Victoria-NSW border.
A ute hit an unmarked police car head-on at Red Cliffs, near Mildura, about 10pm, and a third car hit the rear of the police vehicle.
Preliminary investigations showed the Nissan Navarra veered onto the wrong side of the road into the path of the police car.
Senior Constable Bria Joyce, 25, died at the scene.
A male leading senior constable, 43, an officer for 21 years, was critically injured and has been flown to the Royal Melbourne Hospital.
The driver of the Nissan Navarra ute who was also killed was a 23-year-old man from nearby Cardross.
The third car's driver and three child passengers were assessed and found to be uninjured. Victoria Police Chief Commissioner Shane Patton told reporters on Saturday:
"You become at a loss of words to describe this. It's an absolute tragedy,"
The officers had started a routine highway patrol shift at 6pm that night.
"I can say at this stage there is no indication of any attempt by the police vehicle to be intercepting anyone, no pursuit involved," Mr Patton said.
He said the crash would have a big impact in the police force and wider community, but would be especially hard for local police:
"Attending a fatal collision is a difficult thing for any police officer to do, but when you're actually attending the scene of a colleague in a close-knit tight community that makes it especially difficult."
The Police Association Victoria said the tragedy would ripple through the entire police force. In a statement, Secretary Wayne Gatt said:
"To the colleagues and friends of our fallen member, days like today are the toughest we face in policing. We are thinking of you, and we stand beside you always."
The crash comes just weeks before the two-year anniversary of the deaths of four officers in a crash on the Eastern Freeway in Melbourne.
Major Collision Investigation Unit detectives are investigating and Kulkyne Way was due to be closed for most of Saturday.