The day before Brian G. Fitch Sr. allegedly shot and killed Mendota Heights police officer Scott Patrick, court documents show he told his ex-girlfriend that he was prepared to use deadly force on police.

That detail was unveiled in search warrants filed in connection with the July 30 murder of Patrick, 47, the most senior officer in his department. Authorities allege that Fitch, 39, a career criminal with three warrants out for his arrest, shot Patrick about 12:20 p.m. that day during a routine traffic stop in West St. Paul.

Fitch is scheduled to make his first appearance Friday afternoon in Dakota County District Court on two counts of first-degree murder in Patrick’s death. Previous hearings were postponed as Fitch recovered from surgery for injuries he sustained in a shootout with police hours after he fled the first crime scene.

Fitch also faces multiple charges in Ramsey County, including attempted murder and assault, for the shootout with police in St. Paul. Fitch was arrested after that shootout.

According to search warrants: While looking for Fitch in the hours after Patrick was shot, police spoke to several people who knew him, including his ex-girlfriend. The woman told police that she had been involved with Fitch for the prior two months.

The woman said that she and Fitch argued on July 28, and that she contacted Oakdale police because she suspected Fitch had keys to her home. Fitch was upset about the call, the woman told police. On July 29, Fitch called the woman.

The woman told police that Fitch sounded weird and angry and that he had been using methamphetamines daily.

It was during that call, according to the warrant, that Fitch allegedly said, “If he got stopped, he would go so far as shooting a police officer,” the woman told police.

Fitch’s court appearance Friday comes nine days after an estimated 5,000 people — about 4,000 representing law enforcement across the state and region — attended a somber memorial service for Patrick at St. Stephen’s Lutheran Church.