Speaking by phone to The Associated Press two weeks after he and his wife were ambushed in their pickup truck, Davis said Wednesday that he doubts his wife's attackers will be brought to justice. But he prays for them.
"I miss her terribly, but those people who killed her need to be saved," Davis said from his home in South Texas. "I pray for them, that God will have mercy on them and help them to know him."
"Only God knows why I made it through," he said later. "It's been the most horrible experience of my life."
Davis believes the gunmen wanted his truck and weren't targeting him and his wife, a registered nurse who helped deliver newborns in clinics they built through their Gospel Proclaimers Missionary Association. But now, after speaking publicly about the shootings, Davis said he knows he's a target.
He said a friend called earlier Wednesday to tell him that his home in Mexico was being watched by drug cartel members. A Mexican prosecutor plans to interview Davis on Friday.
"I know it's the drug cartel and the Zetas and the guys who shot at us, shot up my truck and killed my wife," Davis said. "They know who I am."
The couple was returning from a visit to one of their churches when they encountered an illegal roadblock Jan. 26, on a highway just south of the border city of Reynosa. The couple had been pursued 15 times before during their years in Mexico, and Sam Davis decided not to stop.
He then heard gunfire from semiautomatic weapons.
The back window of the truck shattered - and the woman he married more than 38 years ago, whom he described as perfect, fell motionless.
"I felt and heard the impact of the bullet that hit her in the back of her head," Davis said. "She instantly slumped over unconscious ... blood began pouring out all over the console and seat. I laid my hand on her neck and could feel her heart was still beating. But I still had over 70 miles to get to the border."
He drove 137 mph, "but it still seemed like forever" before they made it to Texas. Nancy was pronounced dead at a hospital. She was 59.
Earlier that day, the couple had talked about what they would do if they were ever kidnapped. After hearing about recent violence - tortures, rapes, beheadings - they agreed "we were not going to stop and surrender without fighting. That's why I did what I did," Davis said.
Because of escalating violence, Davis was able to convince his wife to stay behind for the last few weeks when he went into some remote villages to check on their pastors and congregations. After his last trip, his wife told him she couldn't stand being without him. They'd been working in Mexico together for nearly four decades.
"We've been together through thick and thin. She said, 'please let me go, take me with you,'" Davis recalled. Granting that request, he said, is something he'll always regret.
He acknowledged that the shooting "was simply one more in a long chain" of drug-related violence in Mexico. If he could go back in time, Davis said, he maybe would have packed up his family and fled Mexico with other missionaries, then waited for the violence to quell before returning to their work. Through donations, their Gospel Proclaimers Missionary Association supports some 15 churches along a 2,000-mile-long circuit through Mexico.
"We had counted the cost and were very aware that it was going to take our lives, but I didn't know what that would mean," he said.
He has found some solace speaking with Tiffany Hartley, the Colorado woman whose husband was shot by pirates as the couple rode Jet-Skis on a Texas-Mexico border lake. His body was never found.
"To know and sense what we've been through, the trauma of watching your mate be killed, the suffering of that. The agony is beyond words," Davis said.
Yet he wants to continue the mission for which his wife died. The couple has two adult sons and seven grandchildren, and Davis said both his sons have decided to help.
Davis has established a memorial fund to build a new church honoring his wife. He has seen lives transformed as people come to embrace faith, and he wants to keep experiencing that beauty.
"I am not angry with God that my wife is gone," Davis said. "I don't understand why he took her. But I know that he has a plan that is working out and it's part of that plan. And so, I remain committed and surrender to his will even though my heart is hurting and I'm grieving."