Police are searching for a link between the assistant to a murdered corporate executive and the killings of the executive, his wife, their 10-year-old son and their housekeeper inside their Washington mansion last month, court documents show.

Police obtained a search warrant for a vehicle that belonged to 28-year-old Jordan Wallace, a driver for Savvas Savopoulos who was identified in the warrant and by Fox affiliate WTTG. Wallace told police he delivered $40,000 in cash to the Savolpoulos family’s house while they were being held for ransom.

The warrant, obtained by The Associated Press, said investigators were looking for “evidence related to the murder of the four decedents,” including “forensic and physical evidence linking (the assistant) to this offense.”

Wallace has not been identified as a suspect.

The search of the assistant’s car yielded a laptop computer, external hard drives, two backpacks and his passport, among other items, the documents show.

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The only suspect who has been arrested in the case is 34-year-old Daron Wint. Police have said Savopoulos, 46; his wife, Amy, 47; their 10-year-old son, Philip; and a housekeeper, Veralicia Figueroa, were held captive for up to 18 hours before they were killed and their house set on fire May 14. All the victims suffered sharp force injuries, according to police.

Savopoulos was the CEO of American Iron Works, a construction materials supplier based in Hyattsville, Maryland. Wint is a former welder who once worked for American Iron Works, police say. He was arrested May 21. Four other people who were with Wint when he was arrested were detained briefly, but they were released without charges and have not been identified.

Investigators believe there was more than one person involved in the crime, court documents say.

Wallace's car was found a block from the Savopoulous home after the murders, the documents show.

Police also allege in the documents that Wallace changed his story about when and how he delivered the money. At first, he told police that Savopoulos had called him on the morning of May 14 and asked him to deliver the $40,000. But he later told police that he had received a text message from Savopoulos the previous evening asking him to deliver the cash, according to the documents.

Wallace also told police initially that he had received the cash in a manila envelope, but he later said he received the cash in bundles and placed it in a manila envelope when he left it inside a car in the Savopouloses' garage.

The Associated Press contributed to this report.