In 2001, Florida-trained hijackers carried out the worst attack on U.S. soil since Pearl Harbor. Last week, a Florida man's shooting rampage in Orlando became the worst attack on U.S. soil since Sept. 11.

The events bookend a rash of cases that illustrate the state's evolving threat of terrorism, from the highly coordinated outside attack to a harder-to-track danger lurking in local communities, schools, workplaces and places of worship.

Since Sept. 11, Florida has seen more than a dozen high-profile terrorism cases.

The Tampa Bay area endured the saga of alleged terrorist supporter Sami Al-Arian and the case of Sami Osmakac, an Islamic extremist sentenced to 40 years in prison for what authorities said was a plan to kill hundreds of people in the area.

South Florida was home to Jose Padilla, the only American held as an "enemy combatant," who was indicted in 2005 with four Broward County men alleged to be part of a terror cell.

Last year, a man was charged with attempting to use a backpack bomb in Key West. In April, a man was arrested on charges of trying to blow up a synagogue near Miami.

"It worries me," said former Florida Sen. Bob Graham. "It heightens the necessity of us having both the best intelligence of what's happening and the best law enforcement and public security capabilities to prevent those who would come here to do us harm from being able to carry out their goals."

But has Florida become a hotbed?

Not necessarily, experts say. It is ripe for activity and there are likely scores of cases under investigation. With its large, diverse and transient population, Florida is a place where people blend in. A tourist mecca where big cities such as Miami, Tampa and Orlando are international destinations.

However, Florida does not stick out nationally. A number of other areas, including greater New York City, Minneapolis-St. Paul, Texas and California have had a string of cases, according to data compiled by the House Homeland Security Committee. There are Islamic State-related cases in all 50 states.

Critics question some of Florida's cases, including Osmakac's, contending the FBI's growing reliance on sting operations has entrapped mentally unstable or vulnerable people who may not pose a significant threat, consuming resources to prevent the kind of attack that devastated Orlando.

That killer represents a distinct challenge. Authorities say there is no evidence the attack was directed by a group such as ISIS, which claimed responsibility. So-called lone wolves are difficult to track.

"The U.S. has put a lot of money and effort into building up our defenses against large-scale organized, directed attacks. However, this kind of inspired violence doesn't present as many opportunities," said David Sterman, who researches homegrown extremism at the New America Foundation.

Graham co-wrote the congressional report on Sept. 11 and has outstanding questions about what happened in the state, including the sudden disappearance of a Saudi family that lived in Sarasota and had ties to the Venice flight school where two hijackers trained and later slammed planes into the World Trade Center.

About 14 of the 19 men spent time in Florida. "It's stunning to me how little we know about the hijackers, even now 15 years later," said Graham, who is pushing the White House to release a classified section of the Sept. 11 report that focuses on Saudi Arabia.

• • •

Two days after the Sept. 11 attacks that killed nearly 3,000, Omar Mateen, a sophomore at Martin County High School, was celebratory, according to classmates.

"He was smiling like it was his birthday," Robert Zirkle told the Palm Beach Post last week. "He made airplane engine noises. Then he tilted his arms and smashed into his seat, making a crashing noise. He was laughing. Me and about five other guys told him to stop or we were going to beat him up. He stopped." Mateen was suspended, school records show.

Mateen's precise motivations for the Orlando killing are still being uncovered, and some criticize a rush to cast it as terrorism as opposed to a hate crime against gays. He had a history of domestic abuse and anger issues.

"Whatever the motivations of the killer, whatever influences led him down the path of violence and terror, whatever propaganda he was consuming from ISIL and al-Qaida, this was an act of terrorism but it was also an act of hate," President Barack Obama said Thursday while visiting Orlando. The Islamic State is sometimes referred to as ISIL.

Florida Sen. Marco Rubio also traveled to Orlando and said that "confronting the threat of violent homegrown radicalization is one of the greatest counterterrorism challenges our law enforcement and intelligence community face."

But in an interview Rubio said he did not think Florida had unique issues beyond being a populous state. "I'm not sure Florida is disproportionately involved in any sorts of things. Unfortunately on Sunday morning, it did hit us at home."

One expert questioned that assumption.

"I don't think it's just because it's a big state," said Daveed Gartenstein-Ross, a counterterrorism expert at the Foundation for Defense of Democracies. "In several geographic locations you actually have what you could regard as terrorist networks. Minneapolis-St. Paul is one example. In Florida, based on publicly available evidence, it seems likely there is a network of some kind."

• • •

Tampa saw two high-profile cases, both involving the University of South Florida. Professor Sami Al-Arian was accused in 2003 of helping finance the Palestinian Islamic Jihad. The case dragged on for years, and he pleaded to greatly reduced charges of conspiring to aid the PIJ by helping a relative with links to the group get immigration benefits. Al-Arian was deported to Turkey in 2015.

His brother-in-law, Mazen Al-Najjar, a former USF instructor, was deported in 2002 after being accused of ties to Palestinian terrorists. He was never charged.

In 2008, USF student Ahmed Mohamed was sentenced to 15 years in prison for providing material support to terrorists, and he admitted to creating a YouTube video showing how to turn a child's remote control toy into a bomb detonator.

He and a friend, Youssef Megahed, became suspects after being pulled over for speeding in South Carolina. The trunk of their car contained PVC pipes stuffed with a potassium nitrate and sugar mixture. But the government's case against Megahed, whose family came to the United States from Egypt, was weak. He was cleared by a jury.

More recent cases in Florida have come under scrutiny, though the government insists the plots were serious. Osmakac, the Pinellas Park man sentenced in 2014 to 40 years in prison, was accused of attempting to use a car bomb, grenades and a suicide vest to carry out large-scale attacks in the Tampa Bay area.

His lawyers argued he was mentally ill and had been coaxed by the FBI. The FBI provided the money he used to buy weapons (also provided by the FBI). The car bomb came with instructions, in case he didn't know how to use it.

The alleged Key West backpack bomber, Harlem Suarez, was also caught in a sting, an FBI informant providing him with the fake bomb. He came to the attention of authorities by posting pro-ISIS messages on Facebook, though there was no evidence he was in contact with the group.

Michael German, a former undercover FBI agent now with the Brennan Center for Justice's Liberty and National Security Program, says those types of cases raise questions of whether the FBI is "manufacturing" terrorism cases and could actually be hurting attempts to find and prevent serious threats.

"It's pouring resources into investigations where the level of threat is extremely low," German said. "I wouldn't argue in these cases that these individuals don't justify some law enforcement response potentially but a sting operation like that is increasingly resource intensive."

The FBI declined comment for this story. But officials there and in the broader national security community say what happened in Orlando can happen again.

"We have not been able to uncover any direct link between that individual, Mateen, and a foreign terrorist organization," CIA director John Brennan said Thursday. "But that inspiration can lead someone to embark on this path of destruction."

Times researcher Caryn Baird and staff writer Allison Graves contributed to this report. Contact Alex Leary at aleary@tampabay.com. Follow @learyreports.