In the last few hours Krovishey had released an elderly woman, a teenager and a young pregnant woman.
'A 2005 film, Earthlings, everybody should watch it,' President Volodymyr Zelenskiy said in the six-second clip which was later deleted.
Maxim Krovishey, 44, lobbed a grenade out of the vehicle and fired twice at officers during a terrifying 12-hour standoff with police after he stormed the bus at around 9.25am in Lutsk, a city in the northwest of the country.
The Russian-born convict made calls to relatives of those he had taken hostage during the siege, demanding that senior politicians must admit to being 'terrorists' or he would blow up the bus.
Krovishey (pictured) is armed and carrying explosives, officers said in a Facebook statement. Pictured, the assailant released a message ahead of the attack.
In a move to secure the hostages' release, President Zelenskiy said he spoke to Krovishey for around ten minutes and agreed to one of his demands, to promote the animal rights documentary 'Earthlings,' narrated by Hollywood actor Joaquin Phoenix.
The president said he had persuaded Krovishey to first release three of the hostages, including a pregnant woman.
'We agreed that he would release three people and after that I will record a video,' Zelenskiy said.
Zelenskiy had been given the option of launching an assault on the bus, but did not want to risk hostages dying during the attack.
'We have the result - everyone is alive,' he said.
At around 9.45pm local time, police announced that the assailant had been detained and that all remaining hostages had been freed without injury.
The state security service (SBU) published a picture of Krovishey sprawled on the ground with security personnel standing over him after his arrest.
Interior Minister Arsen Avakov said an accomplice of Krovishey was detained in the eastern city of Kharkiv.
Police had blocked off the city centre with armed officers, cars and an armoured personnel carrier while they tried to persuade Krovishey to free the hostages in a day-long standoff.
Photos and footage showed a small bus parked in the middle of an empty street, with at least two windows smashed and others covered with curtains.
Police said Krovishey threw a grenade out of the bus. Avakov said Krovishey had fired shots out of the bus at police.
'The attacker threw a grenade from the bus, which, fortunately, did not detonate,' a statement said.
In posts on social media, Krovishey had also demanded that senior Ukrainian officials publish statements saying that they were terrorists.
Krovishey, a former prisoner who has complained about 'Ukraine's system' in a series of posts online and previously published a book titled Philosophy Of A Criminal, was previously thought to have had 20 hostages.
In a Telegram account reportedly belonging to him, Plokhoy apparently admitted taking people on the bus hostage, said 'the state has always been and always is the first terrorist'.
In his book the hostage-taker wrote: 'You can kill me, but it will not correct me. I am not afraid. The face of God is in the mirror.'
In a video message released ahead of the hostage-situation Krovishey recorded himself holding a gun.
He said: 'Happy anti-system day. Don't fool yourself. Celebrate the truth.'
A statement from the attacker claimed: 'There are a lot of people with me - machine guns, grenades, two bombs.' He said he had an accomplice 'in a crowded area of the city'.
'The man put forward his demands to law enforcers,' said police. 'Negotiations with him are underway. He is being talked to over the phone.'
His demands appeared absurd, calling on senior Ukrainian officials to post videos saying they are 'terrorist in laws'.
He also asked Ukrainian president Zelensky to urge people to watch the 2005 movie Earthlings.
Krovishey was born in Russia - then part of the USSR - in 1975. He was convicted of group robbery in 2013 and is believed to have served three jail sentences, the longest for eight years.
Nicknamed Maxim Bad, the assailant has posted online: 'What is freedom? Heaven. How to get there? Be a criminal.'
He previously wrote a book entitled 'Philosophy of a criminal'.
'My death is not an obstacle for the explosions,' he said. 'The state has always been and is the first terrorist.'
Comment: We've said it many times before: Vegans are crazy.
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