Austria has arrested 14 people between the ages of 18 and 28 in connection with the attack and is investigating them on suspicion of belonging to a terrorist organization, the minister said, adding that the attacker’s actions must also be investigated.

“Before the attack began, some things did not work out, according to available information,” Nehammer told a news conference.

In July, the Slovak intelligence service transmitted to Austria information suggesting that the attacker tried unsuccessfully to buy ammunition from Slovakia, said Nehammer and Director General of Public Security Franz Ruf.

“In the next steps, obviously something went wrong with communications,” said Nehammer, who called for an independent commission to look into the errors.

After receiving the information from Slovakia, Austrian intelligence agencies at the federal and provincial levels made the necessary checks and sent questions to Slovakia, Ruf said.

“It is up to the commission to clarify whether the process went well and in accordance with the law,” the minister said, pressured to say what did not work well.

The perpetrator of the armed attack, who was killed by police a few minutes after opening fire in crowded bars, was a 20-year-old man of Austrian and Macedonian citizenship. Born and raised in Vienna, he had been convicted and imprisoned for trying to reach Syria to join the Islamic State.

All those arrested in this case have a “migrant past,” Nehammer said.

Vienna police chief Gerhard Puerstl said they had dual Austrian and Bangladeshi, Northern Macedonia, Turkey and Russian citizenship.

Witnesses to the attack handed over more than 20,000 mobile phone footage to authorities, which authorities analyzed before concluding that he was a single shooter, Nehammer said, ending the confusion.

Switzerland has also arrested two men, friends of the shooter, in connection with the attack.