Published: Jan 27, 2011 5:53 PM EST
Updated: Jan 27, 2011 2:57 PM EST

PHARR, Texas (AP) - Texas authorities say a U.S. missionary fatally shot in the head in Mexico and driven to the border by her husband may have been targeted because of the couple's expensive pickup truck.

Pharr police chief Ruben Villescas said Thursday that pickup trucks such as the 2008 Chevrolet driven by Nancy and Sam Davis are coveted by criminal organizations in Mexico.

Villescas says damage to the couple's truck suggests that another vehicle tried to run them off the road. He says Nancy Davis was struck in the head by a bullet fired through their pickup's back window.

Nancy Davis was pronounced dead at Texas hospital on Wednesday. Police say Sam Davis told officers they were attacked about 70 miles south of the U.S. border.

(Copyright 2011 by The Associated Press. All Rights Reserved.)