KAUFMAN, Tex. — The contents of a storage unit — and the former elected official who had an associate rent the shed for him — have become central to the investigation into the murder of two prosecutors here.

Investigators arrived on Saturday at Gibson Self Storage in Seagoville, 20 miles from the parking lot where a prosecutor was shot and killed in January. It is also 14 miles from the house where the Kaufman County district attorney and his wife were found shot to death in March. Investigators had learned that a large storage unit at Gibson’s was linked to Eric Lyle Williams, 46, a former justice of the peace who lost a bitter legal battle with the two prosecutors last year and was removed from office.

The storage unit appeared to have been rented at Mr. Williams’s request by an associate of his. Inside, investigators found more than 20 guns and a white sedan that Mr. Williams bought under someone else’s name, according to law enforcement authorities. Investigators questioned Mr. Williams several times after the prosecutors’ deaths, but one official said he had not disclosed to them the existence of the storage shed, the guns or the car, despite assertions by one of his lawyers that he was cooperating with law enforcement.

The sedan was a Ford Crown Victoria that resembled an unmarked police car. Witnesses described a similar model, a silver or gray Ford Taurus, fleeing the scene of the January shooting. And the firearms included two or three handguns and seven assault rifles. The weapon used to kill the prosecutor in January was believed to be a revolver, while the gun used in the shootings of the district attorney and his wife was an assault rifle.