It could have been ignored as a meaningless threat, but one Marriott employee in Long Beach, California, chose to take initiative after a hotel cook threatened to commit a mass shooting.

The employee’s decision to speak out led to the arrest of Rodolfo Montoya, 37, who police say had a stockpile of weapons and hundreds of rounds of ammunition in his home. He was arrested after authorities confirmed he allegedly threatened to kill fellow employees and guests who came into the hotel.

Montoya was reportedly angry about a human resources problem at his job.

“In recent months, we have seen several tragic incidents that have resulted in many lives lost,” Chief of Police Robert G. Luna said in a press statement. “The witnesses who came forward and the diligence of our employees involved in this investigation very likely prevented a threat of violence and saved many lives.”

Jennifer DePrez, a press officer for the Long Beach police department, further tells TIME that the department has always been proactive when it receives reports of threats.

“While this has been more prevalent in mainstream media, this isn’t new to our agency,” she says. “This is something that we have always looked into and taken very seriously.”

Montoya’s arrest is the latest in a wave of incidents in which people have threatened to carry out violent acts since the El Paso and Dayton mass shootings earlier this month left 31 people dead and many Americans fearful that more mass shootings are on the horizon.

Law enforcement and other experts believe that all these threats should be taken seriously.

“In 80% of the mass shooting cases that we studied the person leaked their plans ahead of time and made a specific threat,” Jillian Peterson, an assistant professor of criminology and Criminal Justice at Hamline University, tells TIME. “You have to take them seriously.”

Peterson has done research on mass shootings and says that many shootings appear to be copycats of previous incidents.

There have been at least 27 threats since that deadly weekend, and experts say the idea of “mass shooting contagion” — or someone being inspired by recent mass shootings — is a real concern.

One of these threats came out of Florida, when a 15-year-old posted an online threat to kill at least seven people at his high school.

The Volusia County teen was using a fake name and told local authorities that he was joking. A video posted by the sheriff’s office shows the officials speaking with the teen and his mother, and arresting him on August 16.

In the video, the mother pleads for her teen son, saying that he’s just a kid and was playing a game. But, an officer explains that police take threats like the one the student is accused of extremely seriously.

“How do we know he’s not going to be like the kid from Parkland, or he’s not going to be like the kid that shot up Sandy Hook? We don’t know that,” the officer tells the mom in the video.

Laura Williams, a spokesperson for the Volusia Sheriff’s Office, tells TIME that while violent threats have always been taken seriously, deputies have had to keep a closer eye on the issue in recent years.

“After the Parkland shooting, though, we began being much more vigilant and we had a multitude of threats right after that shooting,” she says.

David Carter, a criminal justice professor at Michigan State University, says that people who are already thinking about committing a mass shooting can be influenced by seeing other attacks.

“It’s almost like a cult mentality. They see someone else accomplish what they want to do and it pushes them forward,” Carter tells TIME. “It infects other people to say ‘Ohh, look what he did. I can do that.’”

Peterson says her research confirms what most people already know –– that mass shootings tend to occur in clusters.

“Almost all of them study other shootings and mimic other shootings. They tend to be socially contagious,” she says.

In the weeks since El Paso and Dayton it might seem there has been a spike in reports of thwarted mass shootings, but experts say that it’s likely a case of both increased threats and more public attention on those threats.

“I think that these threats happen all the time,” Peterson says. “I think other people kind of get triggered by this idea and then law enforcement is under a lot of pressure right now so we’re seeing images of kids getting escorted out in handcuffs for making a threat.”

No mass shootings have been carried out in the wake of the El Paso and Dayton tragedies.

Orange County Florida Sheriff John Mina, who is also a board member for the International Association of Chiefs of Police (IACP), says that along with monitoring extremist web sites and social media, law enforcement is taking all threats very seriously and encouraging people to call them anytime someone makes a threat, even if it doesn’t appear to be serious.

“These days, you can’t take a chance. It could save someone’s life or it could save many, many lives if you call,” Mina tells TIME. “People are seeing law enforcement react very quickly to these threats and making arrests.”

Mina says in the last few years he’s noticed a lot of the threats they encounter are on social media, and when posters are contacted by police they will say they are just kidding. He says people must be extremely careful about what they post online.

“We can’t kid around like that anymore,” Mina says. “There are just certain things you just can’t say.”

However, Peterson says the problem is that once someone makes a threat, the solution can’t just be to arrest the suspect and move on. She says that there needs to be an approach of rehabilitation and help.

“Everybody goes into this planning on dying in the act, so if you think of these as suicidal individuals, threats of punishment don’t work,” Peterson says. “We need to have this approach of what’s going on in this person’s life and how can we hook them up with intervention that’s going to get them out of this place.”

Write to Josiah Bates at josiah.bates@time.com.