(CNN) - Across the country, dozens of suspects have been turned in for mass shooting threats in the three weeks since 31 people died in Texas and Ohio, and police are taking no chances.
At least 27 people were taken into custody after making violent threats or talking about attacks, following a directive from FBI Director Christopher Wray that called for agency offices nationwide to update their threat assessments.
The FBI cited concerns that the mass shooting in El Paso and Dayton could inspire “similar acts of violence” by U.S.-based domestic violent extremists and asked the public to “report to law enforcement any suspicious activity that is observed either in person or online.”
Police in Long Beach, Calif., arrested Rodolfo Montoya, a 37-year-old cook, Wednesday, based on a tip from a fellow employee at a Marriott hotel. Authorities say the man was planning a shooting spree at the hotel.
"A search of the suspect's residence in the city of Huntington Beach led to the seizure of multiple high-powered firearms, hundreds of rounds of ammunition, as well as tactical gear,” said Chief Robert Luna with Long Beach Police.
In Volusia County, Fla., a 15-year-old is in juvenile detention after police say he made an online threat last Thursday to bring a gun to his high school.
Other potential attacks have been thwarted in Tempe, Arizona, and Youngstown, Ohio. Those who made the threats were taken into custody.
The locations of the threatened targets are often similar. Police say in at least nine separate incidents, the targets were schools, and at least five cases involved Walmart stores.
"It's really sad that I have to go to school and think about that and think about the people that are making threats,” said Emily Martinez, a 17-year-old student in Albert Lee, Minn., whose high school was among those threatened.
In addition, at least six of the attacks were allegedly to take place in Florida.
Experts say unusual behaviors and direct threats are some of the red flags to look for in someone who may be planning a mass shooting. Local law enforcement is the best place to report such signs.