The counterterrorism unit is reminding that open areas like grocery stores and outdoor restaurants can be considered high-value targets.
"This mass shooting is a reminder that crowded openly accessible locations such as grocery stores, restaurants, and cafes remain high-value targets for a wide range of violent extremists and ideologically untethered malicious actors," the bulletin said.
They added that warmer weather and the loosening of COVID restrictions nationwide could give people new opportunities for violence after the cancellation of many large-scale events over the last year.
RELATED | Magazine photographer, police officer, soon-to-be grandfather: What we know about Boulder shooting victims
New Yorkers were warned to be on alert for suspicious behavior.
Meanwhile, investigators are still searching for a motive in Monday's shooting in Colorado that left 10 people dead.
Those who lost their lives at the King Soopers store in Boulder ranged from 20 years old to 65. They included a magazine photographer, a Medicare agent with a passion for theater and others going about their days at a busy shopping plaza.
The 21-year-old gunman is expected to make his first appearance in court on Thursday morning.
RELATED | Colorado grocery store shooting suspect prone to rage, delusions: Officials
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