share. >> davis is a former special forces soldier. he's 36 years old. maried from littleton, colorado, sweer lea and we're learning senator kerry has left pakistan and is on his way back to washington. we'll be waiting for an update from him. the u.s. government will not stop helping mexico fight its bloody drug war though immigrations and customs agent was killed there. zapata was driving with another agent yesterday. their vehicle came under fire. one official said the two may have stopped what the appeared to be a checkpoint. zapata was killed, the other agent wounded. and nbc's mark potter is following the story from miami. does mexico know, or are they saying, who was behind that check point or roadblock here, mark? >> reporter: well, hi, contessa. if they do know, they're not saying publicly. what we're hearing from american law enforcement officials and mexican officials that they seem to think the killing is linked