Nine people were killed and 27 others injured including children at a Munich shopping centre on Friday, before the gunman is believed to have turned his gun on himself.
Here's what we know:
Who was the attacker?
The 18-year-old gunman has been named as David Ali Sonboly, a student born and raised in Germany.
The gunman is believed to have acted alone when he went on a rampage at a shopping centre and fast-food restaurant on Friday afternoon.
According to the Bavaria state crime office, the attack had been planned for a year.
He used a semi-automatic 9mm Glock 17 handgun, which had had its serial number illegally removed.
The suspect also had 300 rounds of ammunition in his rucksack when he went on what police have called a "classic shooting rampage".
He did not have a licence to own a gun, and purchased the firearm on the so-called "dark web", police said.
Seven of the nine people killed were teenagers, police said.
are believed to have included three Turkish nationals, a former police officer and a 17-year-old of Greek origin who reportedly saved his sister's life by pushing her out of the way when the gunman opened fire.
Ten of the 27 injured are said to be in a critical condition, including a 13-year-old boy.
Shooter 'hacked Facebook account to send out invitation'
Munich police investigator Robert Heimberger said it appears that the perpetrator hacked a Facebook account to invite people to come to the mall for a free giveaway.
The post, sent from a young woman's account, urged people to come to the mall at 4 pm, saying "I'll give you something if you want, but not too expensive," according to the Associated Press.
Heimberger said: "It appears it was prepared by the suspect and then sent out."
The woman shortly after reported that her account had been hacked.
Police: "No indications" attack was linked to IS
Munich police chief Hubertus Andrae said the teenager's room had been searched and "based on the searches, there are no indications whatsoever that there is a connection to Islamic State".
He also said the attack was not linked to refugees.
Mr Andrae also said initial investigations had not given any reason to believe there was more than one perpetrator and attacker had "nolink whatsoever to the topic of refugees".
He also stressed there was no reason not to visit Munich or to cancel events for security reasons.
Gunman has received treatment for depression
The motive for the attack is not yet known but the gunman had been in psychiatric care and was treated for depression, police said.
Teen was "obsessed with shooting rampages"
Police said documents about "frenzied attacks" had been discovered the gunman's room, including a book entitled "Rampage in Head: Why Students Kill."
Sonboly is said to have been an avid player of violent video games.