Fort Hood , Texas ( CNN ) -- Crime-scene testimony dominated Tuesday 's proceedings in the court-martial of admitted Fort Hood gunman Nidal Hasan , with an FBI agent describing the `` chaotic '' scene of the 2009 massacre . Special Agent Susan Martin , a member of the team that collected evidence from the processing center where Hasan is accused of killing 13 people and wounding 32 , said seven bodies were visible from the moment she walked in the door . The yellow folding cards , known as `` tents , '' that agents carried to mark evidence numbered only up to 100 -- a figure far short of the number of shell casings and bullet holes investigators had to catalog , she said . `` It was very chaotic , '' Martin said . `` There were several bodies in Area Four . There was medical equipment all over the floor . It was a pretty gruesome scene . '' Army social worker thought shooting was an exercise . Investigators had to use adhesive-backed pieces of note paper to identify the evidence scattered across the floor , she said . The FBI ultimately entered 146 shell casings and six magazines into evidence from the scene . FBI Special Agent Brett Mills analyzed the trajectory of 58 of the bullets from five separate shooting locations , calling it `` the worst scene I 've ever seen . '' Agents analyzed the trajectory analysis of more than 270 bullet holes in the building , but could not re-create all of the paths of the bullets because furniture and other evidence was moved in the process of trying to treat victims , they said . Hasan , an Army psychiatrist who was paralyzed by a police bullet during the rampage , admitted at the start of the trial August 6 that he opened fire in the processing center where soldiers were being prepared for deployment to Afghanistan and Iraq . Fort Hood victims feel betrayed . A U.S.-born citizen of Palestinian descent , Hasan had been scheduled to deploy to Afghanistan before the killings . Prosecutors allege the devout Muslim had undergone a `` progressive radicalization , '' giving presentations in defense of suicide bombings and about soldiers conflicted between military service and their religion when such conflicts result in crime . If convicted , he could face the death penalty . In a military capital trial , a guilty plea is not an option . Hasan is representing himself , but with attorneys assigned as stand-by counsel to assist him . Those lawyers requested to be removed last week , saying they believed Hasan was trying to help prosecutors win a death sentence . The presiding judge , Col. Tara Osborn , refused their request Thursday , calling their complaints `` nothing more than their disagreement with Hasan 's strategy in conducting his defense . '' CNN 's Matt Smith contributed to this report .
NEW : `` The worst scene I 've ever seen , '' FBI agent testifies . Agent recounts the `` chaotic '' scene of the 2009 killings at Fort Hood . Army psychiatrist Maj. Nidal Hasan is charged with killing 13 people , wounding 32 . Hasan has admitted he was the gunman ; he 's representing himself .