WASHINGTON, DC (RNN) - Authorities "erred on the side of caution" when seeking other persons of interest in the Washington Navy Yard mass shooting, according to the Metro police chief.
Chief Cathy Lanier said Tuesday police elected to keep residents informed and asked them to shelter in place while they sought two men they thought could be connected to the fatal attack. Both were described as 40 to 50 years old and dressed in military-style outfits.
"We had information we could not dismiss, so we thought that was the most prudent decision at the time," she said.
The men were later cleared, and officials said they believe 34-year-old Aaron Alexis acted alone in the shooting that caused the deaths of 12 people.
Valerie Parlave, head of the Washington FBI field office, spoke on another misconception from the early hours of the investigation. She said they had no reason to believe Alexis ever used the semi-automatic rifle; instead he entered the Naval Sea Systems Command building with a shotgun and took a handgun from someone at the facility.
Parlave reiterated that the shooter used valid identification to get in the Naval complex, which he had from his time as a Navy reservist. She also asked anyone who came into contact with Alexis before the shooting to contact the FBI.
"We have determined Mr. Alexis arrived in the Washington, DC, area on or about August 25 and has stayed in hotels in the area since that time," Parlave said.
She added the investigation continues at the scene, and they are conducting interviews and looking through social media to determine the motivation for the shooting.
Alexis had been treated for mental illness and was hearing voices, according to reports Tuesday.
Sources told the Associated Press the former Navy reservist had suffered serious issues, including paranoia and sleep disorder. The Veterans Administration had been treating him since August, but he had not been declared mentally unfit, the sources said.
That declaration would have caused the security clearance allowing him access to the Navy Yard to be revoked.
On Tuesday, authorities identified the five other people killed as Martin Bodrog, Arthur Daniels, Mary Francis Knight, Gerald L. Read and Richard Michael Ridgell. They ranged in age from 51 to 58 years old.
Among the dead previously named were longtime employees Michael Arnold, 59, of Lorton, VA, a Navy veteran with 29 years of service before retiring for a civilian position last year; Sylvia Frasier, 53, who worked at Naval Sea Systems Command as an information assurance manager since 2000; Kenneth Proctor, 46, who spent 22 years working for the federal government; and Kathleen Gaarde, 63, of Woodbridge, VA, who was a financial analyst supporting the organization responsible for the shipyards.
Also killed were 73-year-old John Roger Johnson, 61-year-old Vishnu Pandit and 50-year-old Frank Kohler. None of the dead were military personnel.
Alexis, a Navy contractor for Hewlett-Packard, opened fire on people at the Naval Sea Systems Command building, killing 12 people, before police fatally wounded him.
CNN reported Defense Secretary Chuck Hagel and other Department of Defense leaders honored victims Tuesday by laying a wreath at the Navy Memorial Plaza.
Police reopened residential streets around the scene of the shooting to general traffic. The Navy Yard remained restricted to "mission-essential personnel" while the investigation continued, the Navy reported via its Twitter account.
The gunfire started about 8:20 a.m. ET, sending military and civilian employees at the headquarters for the Naval Sea Systems Command scrambling.
The FBI said Alexis, a contract employee, had "legitimate access" to the Navy Yard as a result of his work and that he used a valid pass to gain entry.
Alexis received a National Defense Service Medal and a Global War on Terrorism Service Medal during his time in the service, which lasted from 2007 until his discharge in 2011.
His dad told police in 2004 that he was an "active participant in rescue attempts" of the Sept. 11 attacks.
Pat Pundisto, who worshipped with Alexis at Wat Busaya Dhammavanaram Buddhist Center in Fort Worth, TX, described the suspected shooter as "a quiet person and a good person." She said she was shocked by the news of the shooting.
But Alexis, born in Queens, NY, also had a number of run-ins with the law.
In 2004, he was arrested and booked after firing two bullets into the tires of a car and another into the air in Seattle. Three .45 shell casings were found at that scene and entered into evidence.
In 2008, he was booked on a disorderly conduct charge in Georgia. He paid $364 in bond.
In 2010, police were called when a bullet from Alexis' gun went into the apartment of his upstairs neighbor. According to a police report, he claimed he was cleaning the weapon when it went off. Officers found a gun cleaning kit next to the gun.
Alexis was arrested but, in a statement, Tarrant County District Attorney Joe Shannon Junior said "it was determined that the elements constituting recklessness under Texas law were not present."
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