3 people arrested, but no charges yet in his death

• Authorities consider the case of Kevin Quick to be a "death investigation"


• His family reported him missing Saturday after he didn't show for a party


• Three people have been arrested, though none has been charged in his death as of yet

(CNN) -- Kevin Quick, a Virginia auxiliary police captain who went missing a week ago, is dead, authorities said Friday afternoon.

Waynesboro Police Chief Michael Wilhelm reported the 45-year-old's death at a Friday afternoon news conference.

Virginia State Police spokeswoman Corrine Geller said that authorities have not positively identified a body found Thursday, but "due to the time that is now transpired since" Quick went missing and his vehicle being found, authorities now consider this case a "death investigation" rather than a missing-person case.

Arrests made in truck theft, but police captain still missing

While no one has been charged in Quick's death, authorities have arrested three people and linked Quick's vehicle to a Sunday night robbery in which one person was shot.

Daniel Mathis and his sister, Mersadies Shelton, have been charged with grand larceny in the theft of Quick's 1999 Toyota 4Runner. A second sister, Shantai Shelton, was picked up on an outstanding warrant from Louisa County, east of Charlottesville, where Sunday night's armed robbery took place, Geller said earlier this week.

The 18-year-old Mathis also was charged with robbery, malicious wounding and a variety of weapons-related charges in connection with the Sunday night robbery, but no details of that holdup were released.

Quick -- an auxiliary police captain in Waynesboro, west of Charlottesville -- was last seen about 10:15 p.m. Friday leaving the Afton, Virginia, home that he shared with his mother. Authorities said his family believed the officer was off duty at the time and heading to a friend's house about 20 miles away.

But he never made it there. His family reported him missing the following day, after Quick failed to show up for a birthday party for his brother that he'd planned.

His 4Runner was captured by surveillance cameras at automatic teller machines twice. The first time was in the town of Fork Union, about 50 miles from Afton, about 11:40 Friday night; the second was in Manassas, on the outskirts of Washington, on Saturday night, Geller said.

Each time, the same two people were in the picture, she said -- but authorities haven't said which, if any, of those arrested were in the image.

The SUV turned up parked under a carport in Mineral, more than 30 miles northeast of Fork Union, on Monday.

CNN's Marlena Baldacci contributed to this story.