Parkland, Florida — The Federal Bureau of Investigation was warned in September about an ominous online comment by the 19-year-old man accused of killing 17 people at his former high school but was unable to locate him, an agent said on Thursday.

Authorities said the ex-student, identified as Nikolas Cruz, walked into the Marjory Stoneman Douglas High School in Parkland, near Miami, on Wednesday and opened fire with a legally purchased AR-15-style assault rifle in the second-deadliest shooting at a public school in US history.

Cruz may have left warning signs on social media in the form of a comment on a YouTube video that read “I‘m going to be a professional school shooter.” That comment troubled the person whose video Cruz commented on, Mississippi bail bondsman Ben Bennight, who passed it on to the FBI, according to a video he posted online late Wednesday.

“No other information was included with that comment which would indicate a time, location or the true identity of the person who made the comment,” FBI Special Agent in Charge Robert Lasky told reporters. Investigators were unable to find the commenter, he added.

The FBI is conducting an extensive review of how it handled that tip to see if mistakes were made, a federal law official told Reuters.

Wednesday’s shooting was the 18th in a U.S. school this year, according to gun control group Everytown for Gun Safety. It stirred the long-simmering US debate on the right to bear arms, which is protected by the Second Amendment.

President Donald Trump addressed the shooting in a White House speech that emphasized school safety and mental health while avoiding any mention of gun policy.

“It is not enough to simply take actions that make us feel like we are making a difference,” Trump said at the White House. “We must actually make that difference.”

Broward County schools superintendent Robert Runcie called for action on gun laws.

“Now is the time for this country to have a real conversation on sensible gun control laws,” Runcie said.

Democrats in the US House of Representatives criticized the Republican leadership for refusing to take up legislation on tightening background checks for prospective gun buyers.

reuters