French Prosecutor Francois Molins yesterday that one of two jihadists who attacked a church in a Normandy town, and slit a priest's throat, was 19-year-old Adel Kermiche.
Adel Kermiche had been charged with terror links and held before being freed on bail, a source close to the investigation said.
Both men were shot dead by police outside the church in the Normandy town of Saint-Etienne-du-Rouvray.
The source said one of them was known to France's anti-terrorism police and had tried twice to go to Syria in 2015. After his release, he had to wear an electronic monitoring bracelet that allows police to locate him at all times.
He had already threatened to attack a church, according to witness testimony collected in his neighbourhood.
"We knew he wanted to go to Syria," a 60-year-old neighbour of the assailant's family, who added that he "never saw him go to the mosque" that he attended.
The attacker was detained the first time in Germany, while he was on his way to Syria, the source close to the probe said. He was not yet 18 years old at the time.
The second time, which was after he had turned 18, he went through Switzerland, and was detained in Turkey. He was sent back to Switzerland and then France.
He was charged and jailed for associating with criminals with terror links. He was then released and fitted with an electronic monitoring bracelet.
During Tuesday's attack on the church, 85-year-old priest Jacques Hamel had his throat slit and another parishioner was seriously wounded.
"He never spoke to us," said the neighbour. "The last time I saw him was on Friday. He was playing football in his garden."
Another of the town's residents, a teenager who said he knew the attacker, told the RTL radio station that he was not surprised by what happened yesterday.
"He talked about it all the time. He spoke about Islam, that he was going to do stuff like that. He told me two months ago, 'I'm going to do a church.' I didn't believe him. He said a lot of things," said the teenager.
Another resident who said he knew the attacker, however, told the same radio station, "He was a young guy like us. I don't understand how he changed like that."
"What he did has nothing to do with Muslims, he did that of his own accord," he added.