Authorities share a reminder after school shooting: “If you see something, say something”

SHELBY COUNTY, Tenn. -- Investigators are now combing through the social media accounts of a Florida school's suspected gunman.

Police said former student Nikolas Cruz opened fire in a South Florida school killing 17 students and stuff and injuring more.

Law enforcement officials uncovered disturbing pictures on Cruz's Instagram holding knives and guns.

"If you see something and it just doesn't look right, put the call in," said Bob Nations, chief inspector of Shelby County Sheriff's Office Homeland Security.

Nations begs the public to report red flags.

WREG asked Nations what he considered reportable.

"If it looks suspicious, if it looks out of place, if it looks out of the norm to them, or they haven't seen it in the neighborhood before make the call. It's not going to do any harm," he said.

Ben Bennight of D'Iberville, Mississippi said he spoke to the FBI in September about a possible school shooting threat that was posted on his YouTube page.

The username was the same as the Florida school shooting suspect.

He said he never heard from the feds again until Wednesday.

"The Miami field office called me, and the local agents came to my house and asked me for more information," said Bennight. "All I had was the screen shot and the name."

The FBI told CBS News they investigated the comment but wasn't able to identify the person who psoted it.

Nations said sometimes it's hard to track usernames and there are Constitutional laws investigators have to abide by.

He assured us though, every tip is investigated.

"You'd rather have the phone call and react to that than not have it and something bad occur," he said.