Police obtained a search warrant for a vehicle belonging to the 28-year-old assistant, a driver for Savvas Savopoulos
who told police he
delivered $40,000 in cash to the family's house while they were being held for ransom before they were slain.
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 was set on fire last month.
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.