FORT HOOD, Texas — A federal investigator who responded to the 2009 shooting rampage at Fort Hood says the crime scene was gruesome, with bodies and medical equipment "all over the floor."

FBI Special Agent Susan Martin testified Tuesday during the trial of Maj. Nidal Hasan. He's accused of killing 13 people and wounding more than 30 others in the attack at the Texas military base.

Martin says agents found hundreds of pieces of evidence, including 146 shell casings and six magazines, inside the building where the shootings took place.

She says agents eventually ran out of numeric markers and used sticky notes.

The testimony marked a shift as prosecutors begin focusing on forensic evidence. In the trial's first week, prosecutors zipped through 60-plus witnesses, many of them soldiers injured in the attack.