
The gunman, identified as Aaron Alexis, is one of the 12 people confirmed to have died in the shooting Monday morning. Alexis was identified Monday using his fingerprints, officials said.
Tarrant County records show Alexis was arrested in Fort Worth in Sept. 2010 for discharging a firearm in city limits. Fort Worth police filed the report with the Tarrant County district attorney's office, but charges were never filed.
Alexis had begun working as a civilian contractor for the Navy, according to NBC's Pete Williams.
NBC News reports Alexis entered the building using another man's identification card. That person was later taken into custody and was being questioned by police.