WASHINGTON -- Thelast year. But the bureau says it did not have enough information to take action.
About six months before police identified Nikolas Jacob Cruz as the suspected, Ben Bennight saw Cruz's name in the comment section of a YouTube video dated Sept. 24.
"I don't know how many Nikolas Cruzes are on YouTube," Bennight told CBS News.
The comment read, "I'm going to be a professional school shooter."
Bennight, a Mississippi bail bondsman, immediately contacted the FBI and the next day an agent came to his home.
"They took a copy of the screenshot, and uh, I guess they initiated an investigation, I don't know -- I hope they did, and I didn't hear anything else about it until [Wednesday] when they contacted me to meet again," he added.
Robert Lasky is the special agent in charge of the FBI investigation. Thursday afternoon, he said the post was a dead end because it lacked specific information about the time, location and identity of the person who posted it.
"The FBI also conducted internal database reviews and open source checks. No additional information was found to positively identify the person who posted this comment," Lasky said.
But, in 2015 and 2016, Cruz had posted pictures of himself on Instagram with weapons.
Ron Hosko, a former assistant director of the FBI, explained how the investigation may have played out.
"I could take threats like that by the dozen and send them to Quantico every day and say, 'What does this mean?' It seldom means much without the background," he said.
"They have to use their resources efficiently, and the volume of this is frankly overwhelming," Hosko added. "They do not have enough swimmers to swim in the mountain of social media threat."
The FBI says YouTube took down the post last year. The Instagram images of Cruz, armed with weapons, stayed up until after Wednesday's shooting.
In a statement Thursday evening, Instagram said it "immediately deleted the shooter's accounts on Facebook and Instagram" following the shooting. YouTube did not respond to a request for comment.