A suspected gunman, Mohammod Youssuf Abdulazeez, 24, a Kuwaiti-born naturalized US citizen died on Thursday in a fire-fight with police.
Abdulazeez was involved in a shooting that killed four Marines in Chattanooga, Tennessee.
He worked in the Perry Nuclear Power Plant's administrative offices in 2013, said Todd Schneider, a spokesperson for FirstEnergy Corp, which owns the facility were the shooting took place.The suspect worked as an engineer at the Ohio nuclear plant and spent 10 days there before he was let go.
Abdulazeez was a conditional employee dismissed after he received general training on company procedures because, "he did not meet the minimum requirements for ongoing employment", Schneider said.
Schneider did not say why exactly Abdulazeez was dismissed, and would not confirm media reports that he had failed a background check. The plant requires a background check for all employees.
Schneider said Abdulazeez was never granted access to the secure area of the plant. Plant employees alerted management after the Federal Bureau of Investigation identified Abdulazeez as the man who had fired on military centres in Tennessee.
The plant, which is about 56km northeast of Cleveland on Lake Erie, began commercial operations in 1987.
Reuters