SPOKANE, Wash. -

The FBI and Spokane Airport police have joined the hunt for the killer who gunned down a South Hill businessman inside his home last weekend.

Investigators want to know if the man who shot Douglas Carlile to death passed through the airport traveling in or out of the Spokane area.

Detectives asked airport police to search for a white Chevy van, which police released video of to the public earlier this week as a vehicle of interest, in their long term parking lots and to check with car rental companies about the vans in their inventory.

It also appears, according to a warrant used to search Carlile's home, that he had taken the precaution of arming himself with a pair of pistols. A .44 caliber revolver was found on the first floor of his home while a .22 caliber Beretta was found in the master bedroom. Unfortunately Carlile never had the chance to use them to defend himself.

The investigation also indicates the killer may have stalked Carlile and his wife for several days, waiting for them to leave and then slipping inside and catching them by surprise when they returned.

"This case is unusual because we don't have these type of incidents in Spokane where somebody comes into somebody else's house and just shoots them," Spokane Police Captain Joe Walker said at a media briefing earlier this week.

Another thing that's unusual is the killer was able to get inside the home unnoticed when a security sticker on the front door says the residence is protected by Sonitrol, though its not known if the alarm was active when the killer went inside the home.

According to this search warrant the gunman confronted Carlile and fired seven times, shooting him in the face. Carlile's wife was upstairs on the phone with 9-1-1 when her husband was shot.

"I want everybody to know that early indications right now are that is this appears to be not a random attack but rather the victim was targeted," Walker said.

Police have also seized Carlile's phone to find out who he was having his last conversations with and are looking for anyone who has done business with him recently.