A 22-year-old man accused of killing a Muslim teenager with a baseball bat in Virginia on Sunday is an undocumented immigrant who entered the United States illegally, federal authorities said on Tuesday. The man, Darwin Martinez Torres, who was charged with murder in the death of Nabra Hassanen, 17, is believed to be from El Salvador, an Immigration and Customs Enforcement spokeswoman said. The agency said it issued a so-called detainer on Monday with the Adult Detention Center in Fairfax, Va., where Mr. Torres is being held without bail, to keep him in custody in the event that he could...