Mexico City, Mexico (CNN) -- A U.S. citizen was shot to death Sunday in a confrontation with the Mexican military at a checkpoint in Guerrero state, U.S. and Mexican officials said Monday.
U.S. officials said they have received conflicting reports as to whether Joseph Steven Proctor, 32, fired at the Mexican military first.
Proctor died, the U.S. State Department said, when he either tried to drive through the roadblock and the military shot at him or he opened fire as he drove through the checkpoint and soldiers shot back.
Records indicate Proctor recently lived in the metro Atlanta, Georgia, area and has relatives in New York.
A woman who answered the telephone at his New York address and who identified herself as Proctor's mother said she was waiting to hear from U.S. officials as to what happened. The woman, who was crying gently, declined to give her name.
Asked if she had heard reports that her son had fired at the Mexican military, she answered, "I've heard that. I don't believe that."
The woman said she did not know how Proctor died.
"I need their information," she said. "I want to find out what happened."
A spokeswoman at the U.S. Embassy in Mexico City said local officials were investigating the circumstances of Proctor's death, "which are still unclear."
Rodolfo Gomez Fernandez, an official with the Guerrero state prosecutor's office, said "it appeared to be true" that Proctor had been shot by the Mexican military.
Proctor's body was found around 2 a.m. Sunday inside a red pickup truck on the federal Acapulco-Zihuatanejo highway near the town of Cerrito de Oro, the government-run Notimex news agency reported.
The state of Guerrero, on Mexico's southern Pacific coast, is home to Acapulco, a popular tourist destination.
CNN's Laurie Ure and Arthur Brice contributed to this report.