New York (CNN) Almost two years before Sayfullo Saipov used a rented truck to run down cyclists and pedestrians in New York Tuesday, killing eight, authorities had been visiting vehicle rental businesses to help owners recognize suspicious activity.
"We went and did extensive outreach to the truck rental business," said John Miller, New York Police Department deputy commissioner for intelligence and counterterrorism, after an ISIS publication about two years ago mentioned New York's Thanksgiving Day Parade as a possible target for a vehicle attack.
"We visited over 148 truck rental locations in this area. The obvious ones, U-Haul, Ryder, Home Depot ... and talked about suspicious indicators, ways to come forward."
As terror tactics evolve, law enforcement officials have had to learn and adapt.
After deadly truck attacks in France and Germany last year, Miller said the NYPD repeated those contacts with local truck rental companies.
"The industry has had a high level of awareness on this matter from the NYPD," Miller said.
The department has two programs -- NYPD SHIELD and Operation Nexus -- that maintain regular contact with New York area businesses and private security officials to discuss ways terrorists may try to exploit firms like rental truck companies, according to Miller.
Saipov was inspired to carry out Tuesday's assault after watching ISIS videos and closely followed the terror group's playbook for an attack, according to a criminal complaint.
"He appears to have followed almost exactly to a 'T' the instructions that ISIS has put out in its social media channels before, with instructions to their followers on how to carry out such an attack," Miller said.
While al Qaeda in the Arabian Peninsula, based in Yemen, had called for vehicle attacks in the West beginning in 2010, it wasn't until ISIS leaders called for such operations three years ago that they began to occur more regularly, CNN national security analyst Peter Bergen wrote this week.
On October 22, Saipov, rented a truck from a Passaic, New Jersey, store that authorities identified as Home Depot to practice making turns ahead of this week's attack, according to the complaint.
On Tuesday, the 29-year-old Uzbekistan native went to the same store and rented the truck for two hours, with "no intention of ever returning it," the document said.
It wasn't clear if the Home Depot store where Saipov rented the truck had been one of those visited by the NYPD.
Miller said the NYPD also works with the Homeland Security Department and other federal agencies to contact truck rental companies outside New York. The Operation Nexus web page said it involves a nationwide network of businesses and that detectives have visited more than 25,000 firms.
The Virginia-based Truck Renting and Leasing Association, or TRALA, which represents nearly 500 trucking companies throughout the country, said Thursday that its members have been collaborating on security issues with local and federal law enforcement for decades.
In addition, the association and member companies worked with Homeland Security to develop a guide on "counterterrorism and security at truck rental and leasing businesses and, in particular, what could constitute a 'red flag,'" the statement said.
"TRALA members stand in full support of federal, state and local law enforcement agencies and their efforts to prevent the use of trucks for illegal and/or harmful purposes," said Jake Jacoby, president and CEO. "Further, we will continue to work with law enforcement agencies to prevent these types of acts in the future."
While Saipov allegedly began planning the attack a year ago and decided to use a truck two months ago, a federal Transportation Security Administration report said he needed little preparation.
"Vehicle-ramming attacks are considered unsophisticated, in that a perpetrator could carry out such an attack with minimal planning and training," said the TSA report, released in May.
"It is likely that terrorist groups will continue to encourage aspiring attackers to employ unsophisticated tactics such as vehicle-ramming, since these types of attacks minimize the potential for premature detection and could inflict mass fatalities if successful."
In fact, terrorists have carried out 17 known vehicle ramming attacks worldwide from 2014 to 2017, causing nearly 200 deaths and more than 600 injuries, according to the TSA report, which included security tips for truck rental companies.
Such attacks are simple to carry out and largely unstoppable, according to Bergen. Closing access to vehicles to anywhere there are crowds would be an impossible task in crowded Western cities.
"What was once a rarely used tactic has now become a tactic of choice for terrorists who are living in the West, because these attacks simply require the rental or purchase of a suitable vehicle and access to crowds of people," Bergen wrote.
A truck rental at Home Depot costs $19 for the first 75 minutes, requires the renter to be at least 21, hold a current US or Canadian driver's license and pay with a valid credit card, according to the company website.
"As far as the truck rental goes, those interviews are being conducted and ... there was certainly nothing unusual enough to cause anyone to call," Miller said.