The suspect, Saipov Sayfullo. Credit:St Charles Missouri Dept of Corrections Witnesses and the authorities described Saipov shouting "Allahu Akbar" or "God is greatest" in Arabic as he carried out the attack and left handwritten notes in Arabic next to the truck, said a law enforcement official who spoke under the condition of anonymity because the investigation was ongoing. He has been arrested. Saipov was an Uzbeki national who had a green card, the law enforcement official said. He added that Saipov first entered the country in 2010 through Kennedy International Airport, and apparently remained in the United States after that. Another acquaintance said he became religious after he moved to the US. "He became religious on the spur of the moment," Mirrakhmat Muminov, a truck driver and Uzbek community activist who lives in Stow, Ohio, told Reuters.

Authorities stand near a damaged Home Depot truck after its driver mowed several people down in New York on Tuesday. Credit:AP "He started studying religion," he said, adding that Saipov "couldn't get enough" of the religious freedoms enjoyed in the United States after living in the strict confines of Uzbekistan. In Uzbekistan, an authoritarian, predominantly Muslim country in Central Asia ruled by Moscow until the collapse of the Soviet Union in 1991, the practice of Islam is tightly controlled by a government wary of radicalism. Emergency personnel carry a man into an ambulance after the attack near the World Trade Centre in New York. Credit:AP Muminov painted a picture of a man who was struggling to make it in the United States, had few friends, and poor communication and English language skills.

"He was withdrawn, nervous, sometimes aggressive. Because of that he was lonely, he lived in his own world. He was not very popular," said Muminov, who last spoke to Saipov about two months ago. On Tuesday night, US time, law enforcement officials converged on an address in Paterson, New Jersey, believed to be Saipov's home. Police tape kept onlookers away from Saipov's apartment building near Genessee and Getty avenues. Muslim residents walked by and some lamented that the attack was once again damaging to the image of their religion. In a phone interview, Kobiljon Matkarov, 37, an Uzbeki immigrant, said he met Saipov in Fort Myers, Florida, several years ago when Saipov was working as a truck driver. Saipov then moved to New Jersey and began driving for Uber, Matkarov said. "He was a very good person when I knew him," he said. "He liked the US. He seemed very lucky and all the time he was happy and talking like everything is OK. He did not seem like a terrorist, but I did not know him from the inside."

As investigators began on Tuesday to look into Saipov's history, it became clear that he had been on the radar of federal authorities. Three officials said he had come to their attention as a result of an unrelated investigation, but it was not clear whether that was because he was a friend, an associate or a family member of someone under scrutiny or because he had been the focus of an investigation. Over the last two years, a terrorism investigation by the FBI, the Department of Homeland Security, the New York Police Department and federal prosecutors in Brooklyn resulted in charges against five men from Uzbekistan and one from Kazakhstan of providing material support to Islamic State. Several of the men have pleaded guilty. It is unclear whether Saipov was connected with that investigation. After the attack, US President Donald Trump ordered the Department of Homeland Security to bolster the vetting of migrants coming into the US. "I have just ordered Homeland Security to step up our already Extreme Vetting Program. Being politically correct is fine, but not for this!," the President said in a Twitter post on Tuesday night, local time.

It was unclear what specifically Trump was ordering the department to do. Officials there referred questions to the White House, which declined to comment beyond a statement issued earlier in the day. "My administration will provide its full support to the New York City Police Department, including through a joint investigation with the Federal Bureau of Investigation," the formal statement issued in the President's name said. "I will continue to follow developments closely." Loading In a letter of condolence to President Donald Trump on Wednesday, Uzbek President Shavkat Mirziyoyev said Uzbekistan was ready to use "all its resources" to help investigate the New York attack. New York Times, Bloomberg, Reuters