CHATTANOOGA, Tenn. (KRON/CNN) — The 24-year-old man accused in the shooting rampage that took the lives of five service members in Tennessee conducted Internet searches on martyrdom as recently as a day before the deadly attacks, according to a person briefed on the investigation.

The FBI is seeking to interview anyone whom Mohammad Abdulazeez may have had contact with in the 48 to 72 hours before last Thursday’s shootings, the official said.

As the country mourns the deaths of the service members, investigators both here in this country and in Jordan are looking for details into what prompted the attack.

Abdulazeez first shot up a military recruiting center at a Chattanooga strip mall, before driving to a local Navy operations support center. That’s where he launched another attack, killing four Marines and a sailor. The gunman died in a gunfight with law enforcement.

Abdulazeez told a friend that ISIS was “doing wrong” and “it was a stupid group and it was completely against Islam,” the friend, James Petty, told CNN on Monday.

Petty, also said that Abdulazeez taught him how to shoot an AR-15 assault rifle and that the two would practice in the woods.

The revelations about the gunman come as sources told CNN that writings uncovered by investigators indicated Abdulazeez was displeased with the U.S. government, particularly its war on terror.

The writings are not thought to be recent — some are more than a year old, predating a much-publicized trip to Jordan — and should not be considered a diary of any sort, according to a person familiar with the family’s interviews with investigators and a law enforcement official briefed on the investigation.

The writings also include other anti-U.S. sentiments and are consistent with someone who is having suicidal thoughts, the sources said.