On March 3, 1931, in Laredo, Texas, Carter, who was 17, shot and killed 15-year-old Ramón Casiano. After returning home from school that day, Carter was told by his mother that there were three Hispanic youths loitering near their family’s property. Carter left his house, shotgun in tow, to confront the alleged loiterers. After finding Casiano and his two companions, Carter pointed his shotgun at them and ordered them to come with him. Casiano refused and pulled out a knife and asked Carter if he would like to fight. Carter then pointed the shotgun at Casiano’s chest. Casiano pushed the gun aside and asked Carter not to shoot while taking a step back. He was then shot and killed. Carter claimed self-defense, but the presiding judge instructed the jury, “There is no evidence that defendant had any lawful authority to require deceased to go to his house for questioning, and if defendant was trying to make deceased go there for that purpose at the time of the killing, he was acting without authority of law, and the law of self-defense does not apply.” Carter was convicted of murder without malice aforethought (a crime similar to second-degree murder) and sentenced to three years in prison. Subsequently, Carter successfully appealed his conviction with the appeals court, holding that the trial court failed “to submit to the jury appropriate instructions upon the law of self-defense.” When the shooting incident was reported in media in 1981, Carter initially denied that he had killed Casiano before falsely claiming that the shooting took place on his property.

In 1973, federal agents investigated Carter concerning his former employment with the Immigration and Naturalization Service after 40,000 to 50,000 rounds of government ammunition were reported missing. He was called before a grand jury to testify about the matter, but charges were never filed.