What to Know A truck was "intentionally" driven into a crowded holiday market in Berlin on Monday, German investigators said

The NYPD stepped up security in response, deploying its counterterrorism unit to high-profile areas of the city like Bryant Park

Nassau County said it's also upping patrols, although authorities cautioned that there is no imminent threat to the tri-state area

As children sipped hot cocoa and holiday revelers shopped for gifts, the NYPD’s counterterrorism unit kept watch over the Winter Village at Bryant Park on Monday night.

Members of the NYPD Hercules team have been deployed at busy spots across the city after a truck careened into a crowded holiday market in Berlin earlier on Monday, killing at least 12 people and injuring nearly 50 more. German investigators later called the horrific act “intentional.”

Officers suited up with weapons in hand patrolled the Winter Village in stark contrast to the Christmas lights, Santa hats and balsam wreaths lining the market’s stands. It was a sign of the times.

“Police and security everywhere,” said Sam Simpson from Louisville.

“It makes me feel a little bit safer, but I also don’t like seeing giant guns around the kids during the holidays,” Los Angeles resident Chrissy Callahan said.

There were also counterterrorism officers under the Christmas tree at Rockefeller Center, on street corners in Times Square and outside Macy’s in Herald Square. At the holiday markets in Union Square and Columbus Circle, crowds weaved their way from booth to booth as officers looked on.

“I feel a little nervous but you’ve got to live your life,” Lower East Side resident Sara Weiner said.

The NYPD told NBC 4 New York that it is monitoring the developments coming out of Berlin and elsewhere.

Nassau County said that it too is upping patrols in high-profile areas like malls and public transit hubs.

Authorities cautioned that there is no imminent threat to the tri-state area.

Big cities have been fortifying sidewalks since the Sept. 11 attacks, installing bollards and concrete planters designed to prevent vehicles from driving into pedestrians or the side of a building. Parts of Times Square and a two-block stretch of Pennsylvania Avenue in front of the White House have been closed to traffic for years, partly as a precaution against car bombs.

A recent posting in an English-language Islamic State magazine called this year's Macy's Thanksgiving Day parade "an excellent target" for a truck attack. That caused enough concern that police used dozens of sand-filled dump trucks to block streets along the parade route.

The NYPD program involving outreach to trucking companies was ramped up in July after a man drove a rented, refrigerated truck weighing about 20 tons into a crowd in Nice, France.

Since then, the NYPD has reached out to about 140 rental companies and seven truck driving schools in the city, giving them the phone numbers of detectives and encouraging them to use them, said Lt. Lucas Miller, who runs the Intelligence Division program.

The NYPD has received several calls from truck rental operations since the Berlin attack, Lucas said Wednesday. The companies were checking in, not offering tips, "but that's just the kind of communication and interaction we want," he said.

Jake Jacoby, president of the Truck Renting and Leasing Association in Alexandria, Virginia, said his group has worked with the Transportation Security Administration and other federal agencies to combat terror.

The group has distributed a brochure to its members about what should raise suspicions with renters. They include attempting to use cash rather than a credit card and inquiring whether a truck can be modified to carry heavier loads or go faster.

Anybody walking in without a reservation should also get extra scrutiny and possibly be turned away, Jacoby said. The group even suggests asking customers how they plan to use a truck, he said.

"If they have trouble answering that question, that's a red flag," he said.