Senators are questioning whether government officials missed warning signs that could have prevented the deadly shooting spree at Fort Hood.

The incident was examined today by the Senate Homeland Security Commission.

Opening the hearing, Senator Joe Lieberman said the shooting was a terrorist act. Lieberman said his committee's probe will not impede the criminal investigation.

During the hearing, terror analyst Juan Zarate said the Fort Hood tragedy raises questions about whether the U.S. is facing a new wave of terrorism driven by lone wolves.

Meanwhile, a memo from 2007 has surfaced that reportedly lists problems during Hasan's psychiatric training.

NPR reports the memo from the chief of psychiatric residents at Walter Reed Army Medical Center said Hasan proselytized to patients, mistreated a homicidal patient and didn't answer the phone when he was on call.

Officials at Walter Reed sent that memo to Fort Hood in Texas when Hasan was transferred there earlier this year.

Psychiatrists in charge of large private medical programs told NPR they would not hire a psychiatrist who had an evaluation like Hasan's.