Two frightening incidents — both from suspects who were outspoken about their political views.

One ended with nearly a dozen people killed. The other caused scares at offices across the country.

Pipe bomb suspect Cesar Sayoc occupied a van covered with stickers of government leaders, some with targets on them.

"There's a wide gap between offensive political expression and committing a crime or crossing over into a true threat," said Roy Gutterman, Syracuse University communications law professor and Tully Center for Free Speech director.

That gap is what makes crossing the line of freedom of speech tricky.

"It's troubling for law enforcement to try to prevent acts of violence, but from a criminal standpoint, there has to be intent and an act of violence or an objective or intent to actually cross that line to commit an act of violence. You can't just arrest people because they say things that are offensive or outrageous," said Gutterman.

When it comes to the synagogue shooting, the suspect, Robert Bowers, posted moments before: "Screw your optics, I'm going in."

Gutterman says the "I'm going in" is the threat.

"If he was being monitored or tracked, that shows intent to commit a crime, a heinous crime. Even so, unless he was under surveillance, there's very little law enforcement would be able to do to prevent," said Gutterman.

Gutterman says it's easy to look back and see the signs, but hard to pick up on them in the beginning.

"Who's to say that somebody's random rant about awful things or hateful posts will lead to violence? There's plenty of people who spew awful, hateful speech online or in print or at rallies and luckily there's no tragic outcome with all of that, but you only need one," said Gutterman.

That's why it always helps to report anything out of the ordinary.

"Law enforcement can track people. When you have a public social media feed, it's public. Some law enforcement agencies follow social media,” Gutterman said.