Emojis and emoticons are especially popular with the teen set, in part because this appealing artwork can express a complex emotion or sentiment with one simple click. Friend’s dog died? Tearful face. Boyfriend sent flowers? Hearty eyes. Aced an exam? Fist pump!

But when is a winky face a menace? Is poo a serious insult? And is there any legitimate reason to text somebody a knife or gun icon?

With the recent felony arrest of a Virginia middle school student who posted a message on Instagram along with a bomb, knife, and gun icon and the words “Killing” and “Meet me in the library Tuesday,” it’s clear that law enforcement is taking seriously any threat made online, regardless of whether the user intended it as a “joke” by using emojis to heighten or replace written language.

And the penalties are steep: The 12-year-old girl in question is being charged with computer harassment and making a threat against her school, the latter of which is a class E felony that could mean four years in jail — despite her mother’s protestations that the girl is “a good kid who’s never been in trouble.”

Across the country, law enforcement and prosecutors are seeing similar incidents. Most recently, Brooklyn teenager Osiris Aristy was arrested for posting several status updates on Facebook that included threats to kill police officers. His messages, which contained expletives and a list of police precincts, included rounds of ammunition and revolver emojis pointed at police officer emojis.

Aristy, 17, was quickly charged with making terroristic threats, which the New York State Penal Law defines as “intent to intimidate or coerce a civilian population […] by murder, assassination or kidnapping” and thereby causing “a reasonable expectation or fear of the imminent commission of such offense.”

Aristy’s lawyer, Fred Pratt, told NBC News in a phone interview that such laws were put into place after 9/11 and are aimed at preventing "real terrorism," not "kids posting emojis."

His client was "just bragging," Pratt said.

Aristy's defense that he “never threatened to act on” his depiction of guns pointed at police officers was little comfort to cops at local precincts.

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“You make a threat on the Internet, we’re going to be watching,” NYPD Inspector Maximo Tolentino, commanding officer of Bushwick’s 83rd Precinct, told news website DNAinfo. “We are going to attempt to prosecute to the fullest extent of the law.”

“The grand jury dismissed this case because there was no direct threat communicated to the police,” Pratt told NBC News. Aristy was “posting these emojis where his friends could see them. A police officer ‘friended’ him. Aristy didn’t email the 83rd Precinct and tell them he was planning on doing something.”

So, at what point does blockheaded braggadocio become criminal conduct? How can cops determine when shooting from the hip might involve an actual gun? The answer may lie in context.

“When it comes to emojis that could be seen as dangerous or in a negative light, the overall message depends on the other information accompanying it,” said Allison Matherly, a social media expert at Texas Tech University.

“Messages should be examined in their entirety,” Matherly said. “The same applies to overall conversations, or relationships between individuals. When there is a history of bullying or a negative relationship, a gun emoji takes on a different meaning due to that history between the two individuals.”

In the case of Aristy, a lengthy criminal record worked against him. At the time of his arrest in January, the teen was out on bail for a first degree robbery case, with a dozen previous robbery, assault, and weapons charges to his name. Cops also found a handgun and 21 bags of marijuana at Aristy’s home. He is "not a good guy," Tolentino told a local community board meeting, according to DNAinfo, saying that Aristy had previously "targeted this community on numerous occasions."

The Class D felony case was ultimately thrown out of court, but the weapons charges hung on. Aristy is set to remain in Rikers Island until his court date on April 23.

With almost 12,000 gun murders a year in the U.S., including seven kids or teens each day, some people wonder why it’s necessary for smartphones to "pack" a cartoon gun to being with. Case in point: Leah Gunn Barrett, executive director of New Yorkers Against Gun Violence (NYAGV), launched a campaign last year called #DisarmTheiPhone, an attempt to have Apple remove the revolver emoji from its iOS.

“We targeted Apple's gun emoji because [Apple CEO] Tim Cook has spoken out on social issues,” she told NBC News. “We wanted Apple to take a stand on America's gun violence epidemic by publicly supporting federal regulations to keep guns out of the wrong hands."

NYAGV’s Twitter campaign encouraged users to tweet Tim Cook and have him remove the gun emoji from iPhones, to “show America wants stricter access to real guns.”

Many Americans believe that the “emoji gun” issue is taking aim at the First Amendment.

“What’s the point in having the emojis if it’s going to come down to a judge saying whether or not we should be able to use them?!” asked one Facebook user on a thread discussing the Virginia middle school student’s arrest. “Whatever happened to free speech?”

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“I put kisses at the end of my messages or blow kisses ... even being sick. It doesn't mean I'm gonna grab you, smother you in kisses then barf down your nice clean shirt! Pathetic!” commented another.

Am I the only one who uses the urn emoji to add weight to a vague threat? — Taylor (@tayhiggins) March 6, 2016

However, social commenters seemed to conclude that a “better safe than sorry” attitude was the best policy, especially when it came to threats on a school.

“Seems to me if they read that message they would be obligated to check it out and consider it a threat in light of our recent school and mass murders,” wrote one Facebooker. “Reverse the situation, if something had happened and the note had gone ignored?!"

Part of the problem is that emojis are just too simplistic — leaving the threat in the eye of the beholder.

“Emojis do not have one single meaning on their own,” said digital media expert Matherly. “However, this goes both ways. Two emojis together can instantly heighten the worry surrounding a conversation just as easily as they can dispel that concern. An emoji can be taken in whatever way the reader perceives it.”