The man suspected of fatally shooting a doctor and himself at a west Texas veterans’ clinic was a former clerk who had threatened the doctor in 2013, federal officials said Wednesday.

The FBI, which is leading the investigation, identified the gunman in Tuesday’s shooting as Jerry Serrato. Douglas Lindquist, who heads the FBI's El Paso office, says Serrato used a .380-caliber handgun to shoot Dr. Timothy Fjordbak and himself at the El Paso Veterans Affairs Health Care System at Fort Bliss.

Lindquist says Fjordbak had reported Serrato made an unspecified verbal threat against him at an El Paso supermarket.

The FBI has hundreds of potential witnesses, many of whom were patients or would-be patients at the clinic.

"Those people were here seeking medical assistance, so we understand the difficulties that this situation presents to them and we're trying to expeditiously get through those hundreds of witnesses to find out details about this incident," Lindquist said.

The shooting was reported shortly after 3 p.m. local time at the El Paso VA Health Care System clinic, which is part of Fort Bliss in El Paso, Texas. Maj. Gen. Stephen M. Twitty confirmed the details at a news conference Tuesday night.

The VA clinic came under scrutiny last year after a federal audit showed it had some of the nation's longest wait times for veterans' trying to see a doctor for the first time. A survey of hundreds of West Texas veterans last year found that they waited an average of more than two months to see a Veterans Affairs mental health professional and even longer to see a physician.

The VA said in a statement that it "is deeply saddened by the tragic situation that has occurred in El Paso, and we are actively working with our partners at Fort Bliss to investigate this matter."

The Associated Press contributed to this report.