Rear Adm. Robert Chadwick, the commander of Navy Region Hawaii, said the service would evaluate whether security would need to be upgraded ahead of the annual ceremony. About a dozen survivors of the 1941 bombing were expected to attend, along with dignitaries and service members.
Chadwick said he didn't know the motive behind Wednesday's shooting at the naval shipyard within the base. The third victim was hospitalized.
It wasn't known if the sailor and the three male civilians had any type of relationship, or what the motive was for the shooting, Chadwick said.
"We have no indication yet whether they were targeted or if it was a random shooting," Chadwick said.
The sailor was assigned to the fast attack submarine USS Columbia, which is at Joint Base Pearl Harbor-Hickam for maintenance. Details about the sailor were not immediately released.
It wasn't immediately known what type of weapon was used or how many shots were fired. Chadwick said that was part of the investigation. Personal weapons are not allowed on base.
Names of the victims won't be released until next of kin have been notified.
"Our thoughts are with the families of the victims and everyone involved. I can say that we are mobilizing support services for naval shipyard personnel as well as everyone else who may be affected by this tragic event," Chadwick said.
The base went into lockdown around 2:30 p.m. when the first active shooter reports were received. The base reopened a few hours later. Witnesses were still being interviewed hours after the shooting.
The shipyard repairs, maintains and modernizes the ships and submarines of the U.S. Pacific Fleet, which is headquartered at Pearl Harbor. The base is the home port for 10 destroyers and 15 submarines. It also hosts Air Force units.
Hawaii Gov. David Ige said the White House has offered assistance from federal agencies and that the state is also ready to help if needed.
"I join in solidarity with the people of Hawaii as we express our heartbreak over this tragedy and concern for those affected by the shooting," Ige said in a statement.
Mass shootings and gun violence are rare in Hawaii. In 1999, a Xerox service technician fatally shot seven coworkers. In 2006, a man fatally shot his taxi driver and a couple taking photos of the city lights from a lookout point in the hills above Honolulu.
Hawaii had the lowest gun death rate among the states in 2017, according to the Giffords Law Center to Prevent Gun Violence. The islands have strict firearms laws, including a ban on assault weapons and large capacity ammunition magazines.
The shipyard is across the harbor from the wreckage of USS Arizona, which sank in the Dec. 7, 1941, Japanese attack. It's also across from the visitors center, which will host Saturday's ceremony. More than 2,300 Americans were killed in the bombing.
The shipyard has played a key role in naval history, most notably during World War II. Shipyard workers were given just days to repair the USS Yorktown, an aircraft carrier severely damaged during the Battle of the Coral Seat in 1942, because the Navy needed to quickly send the ship to Midway to meet Japanese forces there.
Some 1,400 shipyard workers labored around the clock for almost 72 hours to patch the carrier together. The planes the Yorktown delivered to Midway sank one of the four aircraft carriers Japan sent to the battle and helped destroy two others. The Battle of Midway turned the tide of the war in the United States' favor.