The father of the driver in the Nice lorry massacre said his son had undergone psychiatric treatment in the past.
Mohamed Lahouaiej Bouhlel, 31, was unstable and sometimes violent, his father in Tunisia told RTL.
Monthir Bouhlel said: "He had some difficult times.
"I took him to a psychiatrist, he took his treatments and he said he had a serious illness."
Since his son moved to France, news from him was rare and he had not seen his son for four years.
His last contact was a phone call last week to mark Eid, he said.
"He said hello to everyone, that's all," the father said.
"We didn't notice anything strange.
"Everything he said was normal."
The suspected terrorist was given a suspended sentence in March following a violent altercation on the road, which involved him use a pallet as a weapon.
His lawyer then, Corentin Delobel, said his client appeared normal.
He told RTL: "I could not say 'he is a terrorist, he's an Islamist, he's a radical'."
He added: "It could have been you or me."
The lawyer said there was no sign of psychiatric trouble and his behaviour was typical of someone finding themselves before the court.
Police found his identity card in the truck where he was killed in a hail of bullets.
French prime minister Manuel Valls said the driver a "terrorist linked to radical Islam".
But prosecutors said that Bouhlel was not known to intelligence services.
Chief prosecutor Francois Molins said police risked their own lives trying to stop the lorry as it travelled more than a mile along the promenade.
A search was launched of his former home on Friday morning, as well as his former marital home. He was said to have separated in 2012.
Bouhlel was known to police for delinquency and domestic violence, but was not on a list of radicalised people, according to the Nice-Matin newspaper.
He was reported to have hired the vehicle last Monday, taking the biggest from a fleet of lorries - a 19-tonne truck normally used for removals.
Neighbours described him as withdrawn, saying he was "alone" and "silent".
A cousin of Bouhlel's wife, Hajer Khalfallah, has claimed that Bouhlel was "not a Muslim".
Walid Hamou told MailOnline: "Bouhlel was not religious. He did not go to the mosque, he did not pray, he did not observe Ramadan.
"He drank alcohol, ate pork and took drugs. This is all forbidden under Islam.
"He was not a Muslim, he was a s***. He beat his wife, my cousin, he was a nasty piece of work."