An Uzbek immigrant, who is accused of killing eight people in New York by driving a rental truck down a bike path, became interested in religion after emigrating to the US, a fellow Uzbek who spoke to him two months ago said.
The accused has been identified by a source close to the investigation as Sayfullo Saipov (29).
He had emigrated to the US in 2010 and CNN said he had left a note saying he carried out the attack in the name of Islamic State (IS) and had shouted "Allahu Akbar" ("God is greatest" in Arabic) after the violence.
"He became religious on the spur of the moment," said Mirrakhmat Muminov, a truck driver and Uzbek community activist who lives in Stow, Ohio.
He added that Saipov had previously lived in Tashkent, the capital of Uzbekistan.
"He started studying religion in the United States," said Mr Muminov, adding that Saipov "couldn't get enough" of the religious freedoms enjoyed in the US 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.
Tuesday's attack shines an uncomfortable light on Islamist militancy in Central Asia, which has supplied IS with thousands of fighters.
If the attacker's identity is confirmed, it would be at least the fourth deadly attack by an Uzbek national or ethnic Uzbek in the current year.
Muminov said Saipov had lived in Stow two or three years ago, they had met through the local Uzbek community, and that Saipov had also worked there as a truck driver.
"He was withdrawn, nervous, sometimes aggressive. Because of that he was lonely, he lived in his own world. He was not very popular," he added.
In a letter of condolence to President Donald Trump yesterday, Uzbek President Shavkat Mirziyoyev said Uzbekistan was ready to use "all its resources" to help investigate the attack.