The man shot dead at Paris’s Orly airport in the French capital Paris on Saturday after attacking a soldier was under the influence of drugs and alcohol at the time.
Blood tests have revealed that a gunman had consumed drugs and alcohol.
Ziyed Ben Belgacem, 39, was killed after he put a gun to a soldier's head saying he wanted to "die for Allah".
Investigators are still trying to understand the motive behind Saturday’s assault by 39-year-old Ziyed Ben Belgacem, which led to a major security scare and the temporary closure of the capital’s second-busiest airport.
Paris prosecutors' office said toxicology tests during his autopsy found traces of cocaine and cannabis.
Belgacem also had an alcohol level of 0.93g per litre of blood, nearly twice the legal limit for driving in France.
He is said to have been radicalised in prison, and was on a police watch-list.
He was involved in a shooting and then a carjacking on Saturday before he attacked a military patrol at Orly, Paris's second-biggest airport.
Belgacem's criminal record included convictions for armed robbery and drugs offences, Paris prosecutor Francois Molins told reporters late on Saturday.
In an interview with French radio Europe 1 on Sunday, Ben Belgacem’s father had insisted that his son was not an extremist and that his actions were caused by drink and drugs.
"My son was not a terrorist. He never prayed, and he drank.But under the effects of alcohol and cannabis, this is where one ends up," the father said.
Europe 1 did not give his name.
The father was released from police custody overnight on Saturday, while Belgacem's brother and a cousin were released later on Sunday.