"(He) said he had a wish to come back," said Umida Saipova speaking with CNN in the Uzbek capital of Tashkent.
"(He) said he missed us, we would live together upon his return. He started arranging his return."
Although he longed to come home, he "had no bad thoughts and expressions about America," she said.
Umida Saipova, 27, said she is one of three sisters and was in regular contact with her brother in the United States, though she hasn't seen him in eight years.
Those insights come days after officials said Sayfullo Saipov, 29, intentionally drove a rented truck into cyclists and pedestrians on a bike path in Lower Manhattan, killing eight people
and injuring about a dozen others. He crashed into a school bus and exited the truck brandishing imitation weapons, and a New York police officer shot him and took him into custody, according to a criminal complaint
Saipov closely followed the ISIS playbook, according to the complaint, and he told investigators the terror group had inspired him to carry out Tuesday's attack.
Saipov appeared in federal court Wednesday and didn't enter a plea, a source at the US attorney's office told CNN. He is charged with providing material support to ISIS, violence and destruction of motor vehicles.
Saipov has lived in at least three states since coming to the United States
on a diversity lottery visa in 2010, working alternately as a truck driver and Uber driver.
Yet friends and family said he had shown few signs of being radicalized. One neighbor in Paterson, New Jersey, described him as a peacemaker who calmed everything down during a disagreement six months ago.
Umida Saipova told CNN she is "dumbfounded by what he did." The news was "like a nightmare," she said. "We can't figure out why it happened."
Her brother was a busy father whose third child, a son, was born in August.
"He went to work, came home, his elder daughter went to school, he brought her there on a bike," the sister said.
She said the family had no idea he was radicalized. "He didn't have new friends and only communicated with old friends from Tashkent and colleagues."
According to two of her parents' neighbors, police detained their father after the attack. It is not clear for how long.
Their mother returned from a visit to the United States in June to see her son.
"She noticed no changes, no suspicious signs," Umida Saipova said. "In general, she did not notice. If she had noticed, she would have checked things."
Her mother fainted when she heard about the attack and was hospitalized for several days. She cannot "recover from the shock," Umida Saipova said.
She and her family have been inundated with calls since the attack but they "don't have any answers."
"The truth is he has the right mind in general; he likes Uzbekistan, is hard-working. He always talked about his Uzbekistan, about the motherland, had no bad thoughts in his head," she said.
"I would like ask my brother what was the reason. Maybe he would tell his kin why and what he did that for."