There were seven victims in total – including an unborn baby.
Eight other people were wounded, including four seriously, in Thursday evening’s attack, said Hamburg interior minister Andy Grote, calling it “the worst crime in our city’s recent history”.
Police identified the gunman as Philipp F., 35, a former member of the Christian group who left the community about 18 months ago “but apparently not on good terms”.
Investigators were still seeking a motive for the killings, but there was no indication of a terrorist motive in the killings, said a senior prosecutor.
The gunman entered the Kingdom Hall building when around three dozen people were attending a service and another 25 people had joined on livestream.
The first distress calls reached emergency services at 9:04 pm on Thursday, and police forced their way into the Jehovah’s Witness building minutes later.
The police action interrupted the shooting, prompting the attacker to flee to the first floor of the building where he killed himself, said Grote.
“We can assume that (the rapid police action) saved many lives,” he added.
Police had initially said the shooting left eight people dead, but that included the gunman and a seven-month-old foetus of killed in the attack. The woman pregnant with the baby has survived
An anonymous tip-off had been sent to the weapons control authority in January this year, claiming that Philipp F. may have been suffering from an undiagnosed psychological illness and that he had a “particular anger against religious members or against the Jehovah’s Witnesses and his former employer”.
Raids following the shooting on the gunman’s apartment uncovered 15 magazines loaded with 15 bullets each and four further packs of ammunition with about 200 rounds.
READ ALSO: What we know so far about the shooting in Hamburg
‘Filmed the whole thing’
The Jehovah’s Witnesses in Germany association said it was “deeply saddened by the horrific attack on its members”.
Neighbours recalled hearing multiple shots fired late Thursday.
“Our son filmed the whole thing, he could see quite well from the house,” Bernd Miebach, a 66-year-old business owner, told AFP.
“On the video you can see that someone broke a window, you can hear shots fired and see that someone broke in.”
Police have asked witnesses to come forward and upload any pictures or videos they may have to a special website.
Another resident said police arrived on the scene within “four or five minutes”.
“We heard shots and we knew something big was happening,” said the woman, who gave only her first name Anetta.
She said she knew the building was used by members of the Jehovah’s Witness community, describing them as “very peaceful, quiet”.
The three-storey building was still cordoned off on Friday with several officers standing outside.
The port city’s mayor, Peter Tschentscher, expressed shock at the shooting.
Sending his sympathies to the victims’ families, he said emergency services were doing their utmost to clarify the situation.
German Chancellor Olaf Scholz said early on Friday that his thoughts were with the victims and their families.
“Several members of a Jehovah community fell victim to a brutal act of violence last night,” Scholz tweeted. “My thoughts are with them and their loved ones.”