The crash happened just after 10 p.m. Saturday near Juniper Avenue and Orange Way.
The driver of the Honda Civic, 62-year-old Jose Landaverde, died at the hospital. His mother-in-law was critically injured, and his wife ended up with serious bruises.
The officer was hospitalized with non-life threatening injuries and was expected to recover. His name had not been released.
The widow said she doesn't remember much about the crash. They had been married 40 years.
At least one witness said the police car did not have its sirens and lights on.
"He didn't have a light, he was just going fast and then he just hit (the car)," the witness said. "As soon as he hit it, he turned them on."
The family just wants answers.
"It's really hard. I'm still just trying to understand why this happened," said Landaverde's son, Elmer.
The San Bernardino County Sheriff's Department was investigating the fatal crash.