PARKLAND, Florida - The FBI says it failed to investigate a specific report in January that Nikolas Cruz could be plotting a school shooting.

The agency said Friday that the tip should've been investigated thoroughly because it was a potential threat to life. Cruz has been arrested and charged with killing 17 people at a high school earlier this week.

On Jan. 5, a tipster who was close to Cruz called the FBI and provided information about Cruz's guns, desire to kill people, erratic behavior and disturbing social media posts. The FBI says the caller expressed concerns Cruz could attack a school.

The FBI was also notified about a comment on a YouTube video posted by a "Nikolas Cruz" last year. It investigated the comment but did not determine who made it.