More than 30 people who experienced or knew of Nikolas Cruz's worrying behavior didn't report it until 17 people were killed in a school shooting in Parkland, Florida, earlier this year.

Cruz's behavior was "troubling ... and in many cases it probably should have caused them to report what they heard, saw or learned," Pinellas County Sheriff Bob Gualtieri said Tuesday, according to The Sun-Sentinel. "But for a variety of reasons they did not."

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Gualtieri, who also chairs the Marjory Stoneman Douglas High School Public Safety Commission — which was created after the massacre at the school — disclosed the news Tuesday as the commission opened four days of hearings.

Cruz, the suspected shooter, reportedly engaged in questionable behavior long before the mass shooting in February -- including killing animals. According to a sheriff's office detective, Cruz once showed another student a photo of a decapitated cat.

The 20-year-old also allegedly "said he was glad they killed all those gay people" in reference to the Pulse nightclub shooting in Orlando, which left 49 people dead.

Cruz also reportedly "made bad jokes about Jewish people, Nazis and Hitler and wished all Jews were dead" and said "he did not like black people and would like to shoot them."

Days after the massacre, the FBI admitted to receiving a call about Cruz in early January. The person called their Public Access Line (PAL) tipline to express concerns about his erratic behavior and social media posts.

The FBI said in a statement at the time that "under established protocols, the information provided by the caller should have been assessed as a potential threat to life" and that protocols were not followed after they received the tip.

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The parents of Jaime Guttenberg, a student who was killed in the massacre, filed a lawsuit against the FBI on Tuesday because the tip wasn't acted upon.

“Everybody failed, and this is going to be the shooting where we hold people accountable,” Guttenberg's father, Fred, said at the hearing on Tuesday, The Miami Herald reported. “If only one person had stepped up and done their job, my daughter would be alive today."

The Broward County sheriff said after the shooting said at least "20 calls for service" were made regarding Cruz in the last few years alone.

Gualtieri reiterated on Tuesday that if you "see something, say something."

"It means something, and it has to be more than a phrase,” Gualtieri said. “We need it to resonate with the public because law enforcement simply cannot be everywhere at the same time, and we have to have the public’s help to effectively do our job.”

The sheriff's detective said that while two students did report Cruz to school administrators in December 2016, they were ignored.