NICEVILLE — A federal postal inspector has filed papers in federal court in Pensacola seeking permission to search the contents of a package sent by Frederick Franken Sr. — charged with murder in the March 15 stabbing death of his 3-year-old son — to his daughter on the Caribbean island of Aruba.

According to the nine-page search warrant application filed with the federal magistrate judge in Pensacola on Friday, the U.S. Postal Inspection Service believes the package may contain a cellphone used by Franken in the hours before he allegedly killed his son and then also stabbed himself at the family home in Niceville.

Franken was arrested and charged with homicide on March 23 at Fort Walton Beach Medical Center, where he was undergoing treatment for his self-inflicted injuries.

The warrant application, which suggests authorities are concerned with possible evidence tampering, notes that Franken and his wife, 38-year-old Eglin Air Force Base airman Darrelly Franken, "were engaged in a conversation throughout March 15, 2019, the date of the incident, until around 3 p.m."

The two last spoke at 3:10 p.m. March 15, at which point Darrelly Franken told investigators she heard her husband "discussing something about $200 ... ." That amount, according to the search warrant application "is the value of the insurance for the subject parcel" as noted on a U.S. Postal Service receipt found during a search of the Frankens' home.

The application goes on to note that Okaloosa County Sheriff's Office investigators are interested in two text messages apparently sent by Frederick Franken to his wife. The messages, sent between 6:20 a.m. and 6:45 a.m. on March 15, "said 'you will see this afternoon,'" according to the search warrant application. The application goes on to state, however that the quote "is not exact, as the text messages were written in Papamiento, the language of Aruba where they are from."

The messages were translated for authorities by Darrelly Franken, according to the warrant application.

Frederick Franken's cell phone was not found during a search of his person, the residence or his car, according to the warrant application. The application also goes on to note that the package that is the subject of the search warrant request, postmarked March 15 with Franken's daughter as the recipient, lists "phone" among the items sent to Aruba.

But according to the search warrant application, Franken's daughter told Okaloosa County Sheriff's Office investigators "she was expecting a parcel that contained car parts" from her father.

At some point in the investigation, the application notes, the package was intercepted by postal inspectors in Miami, and it is now at the Postal Inspection Service office in Pensacola as a judge's decision on the search warrant application is pending.

The Okaloosa County Sheriff's Office's investigation into the death of 3-year-old R.J. Franken is continuing, according to spokeswoman Nicole Wagner, who said the Sheriff's Office does know about the Postal Inspection Service's search warrant application tied to the case.

"We're aware of it, and we're working with them," Wagner said.

Frederick Franken was booked into the Okaloosa County Jail on March 26, and remains there after being denied bond, according to jail records.