The 27-year-old German man is suspected of storming a synagogue in Halle on Wednesday and shooting a female passerby, before attacking a nearby Turkish kebab shop where a man died.
Balliet broadcast a live video of the attack on the Twitch streaming platform and published an antisemitic and racist “manifesto” online, echoing the Christchurch terrorist and other recent far-right attackers.
He repeatedly called himself a “loser” in the footage for failing to break into the synagogue or kill more people, after his homemade gun repeatedly jammed.
The livestream stopped after Balliet dumped the helmet-mounted camera and his car while fleeing Halle, before hijacking a taxi and being arrested following a crash around 10 miles south of the city.
“What we experienced yesterday was terror,” Germany’s chief federal prosecutor Peter Frank told a press conference, saying the suspect was motivated by “antisemitism, xenophobia and racism”.
“He wanted to mimic similar acts that happened in the past, and he also wanted to incite others to copycat his actions,” he said.
Mr Frank said the weapons used were “apparently homemade” and 4kg of explosives discovered in the car were built into “numerous devices”. He said the suspect used the dark web.
Investigators, who are searching through material from Balliet’s home, are looking into how he was radicalised, how he obtained materials for the weapons and explosives, and whether anyone else knew of his plan.
Balliet is accused of two counts of murder and nine of attempted murder, and remains in custody.
Local media reported that Balliet is from the Saxony-Anhalt region of Germany, and a document posted online said he had driven 45 minutes to the synagogue from his home.
Der Spiegel reported that he had no criminal record and lived with his mother in Benndorf, where neighbours said he led an “isolated life”.
A source told Reuters that Balliet had done military service, which was compulsory in Germany at the time, but received no special training.
Balliet’s livestream and online documents seen by The Independent suggest he was deeply embedded in online forums, gaming culture and had a fascination with Japan.
He called himself a “weeb”, denoting an obsession with Japanese culture, and an “anon” – the term used to describe users of 4chan, 8chan and other imageboards that were used by previous mass shooters to share manifestos.
One of three documents Balliet posted online before the attack was entitled “manifesto” in Japanese and included an image of a sexualised anime “cat-girl”.
The tongue-in-cheek message said that readers could get a free cat-girl or “waifu” if they “kill at least one Jew”.
The document, written in English, called for “discontent white men” to murder Jews, non-whites, communists and “traitors”.
Another document linked to Balliet’s livestream on Twitch, which is predominantly used by gamers to broadcast online play.
The third, also written in English, contained details of Balliet’s preparations for the attack and included images of his six guns, which he claimed to have made or modified himself.
Balliet also listed homemade ammunition and improvised hand grenades, smoke grenades, pipe bombs and small explosives, which he said he had “prepared months in advance”.
The document said he aimed to inspire attacks by “other suppressed whites” by livestreaming his attack, kill as many “anti-whites” as possible, and that he would wear protective clothing and aimed not to die.
It included a score sheet of “achievements” for the attack, including numbers of kills and methods, but few were met.
The documents appear to have been originally posed on the Kohlchan website, which is a predominantly German-language “chan” imageboard whose name translates as “cabbage chan” or “nonsense chan”.
Balliet said he had “originally planned to storm a mosque or an antifa ‘culture’ centre” which he thought would be less secure than the synagogue targeted.
But he claimed his ultimate target was Jews, after declaring his belief in conspiracies including the “Zionist-occupied government” theory.
Speaking in English at the start of his livestream, Balliet said he was a Holocaust denier and said he believed feminism was ”the cause of declining birth rates in the west”.
There were initially fears that more than one attacker was at large, following numerous witness reports of shootings in different locations, but police wound down an extensive search operation on Wednesday afternoon.
Local police said Halle and the Saale region had been given the “all clear” by security forces, following a manhunt where public transport hubs were closed as residents were ordered to stay inside for their own safety.
Holger Stahlknecht, the interior minister of Saxony-Anhalt, said the suspect managed to drive out of Halle following an exchange of shots with police that left him with a neck wound.
He abandoned his car in a small nearby town, where he shot and wounded two other people. He continued southward in a stolen taxi, and was arrested as he left that vehicle following a car crash.
The attack came during Yom Kippur, a Jewish religious festival that sees observers fast and pray to atone for sins.
A spokesperson for the local Jewish community said up to 80 worshippers were inside the synagogue at the time, but security measures at its entrance “withstood the attack”.
Several people were injured in the shooting. Balliet had opened fire at random in Halle, but many of those seen in the video, including an elderly cyclist and passing motorists and pedestrians, were spared.
The footage been removed from the Twitch website but is being spread online on “chan” websites, mainstream social media and the encrypted Telegram messaging application.
Apart from asides and frequent cursing in German, Balliet spoke English in the livestream and also wrote all three documents he posted online in English.
A livestream was also made by the Christchurch shooter, who used Facebook Live, and posted a “manifesto” espousing a theory that white people are being eradicated from western nations on the 8chan image board.
The attack inspired copycat terrorists around the world, including in the UK, Norway and the American cities of El Paso and Poway – where a synagogue was attacked.
On the 4chan website, some posters were comparing the Halle shooter to “Saint [Brenton] Tarrant”, while another wrote: “Kill society, one lone gunman at a time. F***, I’m lovin it.”
Others ridiculed the shooter for failing to kill more victims and using homemade weapons.
A right-wing extremist chat group dedicated to Tarrant urged followers to “learn from others’ mistakes” when launching future attacks.
As officials sought to reassure the Jewish community and address concern about rising right-wing extremism, Germany’s president visited the scene of the attack in Halle and urged his nation to stand up for its Jewish compatriots.
“It is not enough to condemn such a cowardly attack,” Frank-Walter Steinmeier said. “It must be clear that the state takes responsibility for the safety of Jewish life in Germany.”
He added that “history reminds us, the present demands of us” that Germans must stand by their Jewish compatriots. “Those who so far have been silent must speak out,” he said.
Justice minister Christine Lambrecht said right-wing extremism “is one of the biggest threats facing us” and vowed to take action on online platforms containing material that incites hatred.
Chancellor Angela Merkel said Germany must crack down on hate, violence and hostility.
“I am, like millions of people in Germany, shocked and dejected by the crime that was perpetrated in Halle,” she told a trade union congress in Nuremberg.
Germany's domestic intelligence agency said the number of antisemitic acts of violence rose to 48 last year from 21 the previous year.
The number of known far-right extremists rose by 100 to 24,100 people last year, with more than half of them considered potentially violent.