Editor's Note: This story includes raw video from the Kenya Mall attack that may be too graphic for some readers.
NAIROBI, Kenya (AP) -- Quiet and respectful at the mosque as a boy, Hassan Abdi Dhuhulow later became angry and radicalized, people in the coastal town in Norway where he grew up said Friday of the Somali native -- the first Westgate Mall attacker to be identified.
Security camera images show the 23-year-old and three other gunmen firing coldly on shoppers as they made their way along store aisles after storming the upscale mall four weeks ago Saturday.
Until recently, investigators had referred to the attackers only by the colors of their shirts. However, two officials in Nairobi, one Western and one Kenyan, confirmed Friday that one of the gunmen had been identified as Dhuhulow.
The suspect's 26-year-old sister, reached in the southern Norwegian town of Larvik, said his family was unaware of any role he may have played in the four-day siege that killed at least 67 people.
"I don't want to believe this. I don't believe that this is him. It doesn't look like him. It isn't him," Idman Dhuhulow told The Associated Press from the quiet town of 40,000 nestled between mountains and the sea, where Dhuhulow lived after his family moved there from Somalia in 1999.
She said her brother went to the Somali capital of Mogadishu for a three-month visit in 2009, then moved to Somalia for good in March of the following year.
He had been studying economics in Norway and "his plan was to go back to Mogadishu and study there," she said.
"We had the best relationship that you can have. He was nice and careful," she said, adding that she had read media reports that he had become radicalized but "that's not something I saw."
Mohamed Hassan, a leader in the Somali immigrant community in Larvik, also described Dhuhulow as respectful to his elders as a young boy and teen.
"He was a quiet, lovable boy while he was here. I never saw him fight other young boys. He was not a troublemaker here in Larvik," Hassan said.
However, others recalled a different Dhuhulow.
Bashe Musse, a Somali Norwegian community leader in Oslo, said Dhuhulow had become radicalized in the years before he left Norway. And another man, who would give only his first name Yussuf, also said a man he believes was the Norwegian-Somali gunman was associated with "pretty radical" circles in Norway.
"He was mad. He didn't feel at home in Norway," said Yussuf, who declined to give his last name for fear of reprisals from sympathizers of al-Shabab, the Somali militant group behind the mall attack.
Yussuf said he met the man he knew as Abdi in 2008 in Oslo and had not had any contact with him since, but several people he knew recognized him in the closed-circuit TV footage of the mall attack.
"We said that it could be him when we looked at the video," Yussuf said.
The newly released images from the mall's security cameras show four men armed with AK-47 rifles cold-bloodedly firing on defenseless shoppers. At one point, a gunman is seen shooting a man trying to hide behind a statue of an elephant. Bleeding profusely, but still alive, the man squirms. Then another gunman comes back and finishes him off.
In other scenes, terrified shoppers and employees are seen scrambling for safety, some scuttling like crabs, as tracer bullets flash overhead.
Authorities have so far been unable to identify any of the assailants from the bodies pulled from the rubble of the mall, where a raging inferno tore through its main department store and a roof parking lot collapsed.
Charred human remains recovered Thursday were awaiting forensic tests Saturday to determine if they belong to the attackers. They filled two plastic containers measuring a foot wide and a foot across, and were recovered along with four AK-47 rifles from a section of the mall that collapsed as security forces battled the terrorists, authorities said Friday.
Johansen Oduor, the chief Kenyan government pathologist, said he didn't know if the remains were those of two bodies or three because the remains were sealed and he hadn't seen them yet.
The Somali Islamic militant group al-Shabab claimed responsibility for the Sept. 21 attack, saying it was in retaliation for Kenya sending troops into Somalia to go after the extremists. Kenyan officials initially said it was carried out by 10 to 15 gunmen, but the security camera video shows only four. A police official said three suspects are in custody, though none directly took part in the attack.