A grief-stricken Victorian man has told how he watched his 19-year-old girlfriend die after a Valentine's Day hit-and-run near the Mornington Peninsula last night.
Ben Taulaga broke down as he taped a farewell letter and a photo of the couple to a telephone pole in Somerville, near where the collision occurred, before kissing the picture.
"She's my love, this sucks, this really sucks," Mr Taulaga told Nine News.
"She was the best girl, she was a strong girl.
The letter said: "Baby Girl, R.I.P, Love forever and always."
Mr Taulaga said that the pair had been walking through a paddock.
"I didn't see who hit who, I just saw her on the ground injured, and she just died on me," he said.
Mr Taulaga's girlfriend was struck by a small truck which was travelling north on Frankston-Flinders Road at about 8.45pm (AEDT).
The truck driver failed to stop and the woman died at the scene despite frantic efforts by paramedics, who worked on her for 30 minutes.
Mr Taulaga said he did not believe the collision was an accident.
"If it was an accident, the person would have stayed, so I don’t think this was an accident," he said.
"Whoever did this, you’re going to pay for it."
Detectives have appealed for the truck driver and witnesses of the crash to come forward.
The truck is described as a light-coloured older model.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or visit.
For more on this story, watch Melbourne Nine News on the Nine Network or online at 6pm.