Just Wednesday, parts of the capitol in Washington DC were locked down after a suspicious letter to the president field tested positive for ricin.
It's the second letter in two days that's tested positive for that poison. The first was addressed to a Mississippi senator. The threats on top of the attacks have Americans on edge and the FBI on alert.
If you look at the terrorist attacks that happened over the last dozen years or so in the U.S., they targeted big and small cities all over the country.
"It shows just how difficult it is to protect these kinds of venues that have large mass gatherings," said Fred Burton, vice president of intelligence for Stratfor, a global information gathering firm in Austin.
We are never 100 percent safe. It's scary, hard to hear but true -- that's the message from Burton.
"We've had similar kinds of mass casualty plots in Times Square, the New York City subway, the DC subway. And of course, we also had the former soldier who was picked up in Killeen who also had a pressure-cooker kind of IED," Burton said.
And there is still a threat in Texas.
While the Department of Public Safety wouldn't go on camera to discuss specific tactics in combating terrorism, we did learn from the agency's 2013 safety threat overview that "Texas continues to face a general threat by lone individuals and also by foreign-based entities," and that "the threat of terrorism and criminal violence is posed not only by religiously motivated extremists from abroad, but also by American domestic extremists."
The 9/11 and the '93 World Trade Center attacks were foreign. Oklahoma City 18 years ago, Columbine four years later, and Sandy Hook last December were domestic. No amount of preparation of assessment stopped them.
And despite best efforts, Burton says we all always need to keep up our guard.
"All of us should be aware after 9/11 of the potential vulnerability that exists in, not only while flying in a commercial aircraft, but at a basic street crime level of just what we call here at Stratfor situational awareness," he said.
The Department of Public Safety is in charge of emergency response of homeland security in the state of Texas but they say whenever there is a large event, like Fiesta in San Antonio this weekend or the Houston marathon in January, it is local law enforcement that always takes the lead. DPS provides support, training and ongoing information throughout the state of Texas.
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