Officials are exploring capital murder charges.

Chief Greg Allen of the El Paso Police Department said officials were exploring potential capital murder charges for the suspect.

The F.B.I. is currently reviewing evidence to determine whether to move forward with federal charges, but Emmerson Buie Jr., the special agent in charge, said that the F.B.I. had not determined whether the shooting was a hate crime, another federal crime or an act of domestic terrorism. Currently the case is a state murder investigation.

[For the latest updates, read our live briefing on the Dayton and El Paso shootings.]

Authorities are investigating a manifesto in connection with the shooting.

Law enforcement officials are studying an anti-immigrant manifesto to determine whether it was written by the gunman, according to a local law enforcement official who has been briefed on the investigation. Given the manifesto’s racially extremist views, it could make the killings a federal hate crime or an act of domestic terrorism if officials determine that it is tied to the shootings.

It declares support for the gunman who killed 51 in Christchurch, New Zealand, outlines fears about Hispanic people gaining power in the United States and appears to discuss specific details about elements of the attack, including weapons.

“Hispanics will take control of the local and state government of my beloved Texas, changing policy to better suit their needs,” the manifesto said. It added that politicians of both parties are to blame for the United States “rotting from the inside out,” but that “the heavy Hispanic population in Texas will make us a Democrat stronghold.”

Twenty-six were injured.

Officials said that at least 26 people were wounded in the attack. Marcelo Ebrard, the secretary of foreign affairs of Mexico, said six Mexican nationals were among the injured. Mr. Ebrard identified three by name: Mario de Alba Montes, 45; Olivia Mariscal Rodriguez, 44; and Erika de Alba Mariscal, 10.

Local hospitals are treating patients from the scene. Victor Guerrero, a spokesman for Del Sol Medical Center, said the hospital was treating 11 victims. Nine were in critical but stable condition and two were stable, he said. Patient ages ranged from 35 to 82.

The University Medical Center of El Paso received 13 patients, according to Ryan Mielke, the hospital’s spokesman. He said two minors, including a two-year-old, were stabilized and transferred to El Paso Children’s Hospital. Mr. Mielke said the victims’ conditions ranged from minor injury to fatal.