The body of Japan's former Prime Minister Shinzo Abe was returned to Tokyo on Saturday after he was fatally shot during a campaign speech in western Japan a day earlier.

Abe was attacked in the city of Nara and airlifted to a local hospital but died of blood loss despite emergency treatment including massive blood transfusions.?

Police arrested the attacker, a former member of Japan's navy, at the scene on suspicion of murder.?

Police confiscated the homemade gun he used, and several others were later found at his apartment.

The attacker told investigators he plotted the shooting because he believed rumours that Abe was connected to an organisation that he resents, according to police.?

Japanese media reported that the man had developed hatred toward a religious group his mother was devoted to.?

The reports did not specify the group.

A black hearse carrying Abe's body and accompanied by his wife, Akie, arrived at his home in Tokyo's upscale residential area of Shibuya, where many mourners waited and lowered their heads as the vehicle passed.

Abe's assassination ahead of Sunday's parliamentary election shocked the nation and raised questions over whether security for the former prime minister was adequate.

Police on Saturday said autopsy results showed that a bullet that entered Abe's upper left arm damaged arteries beneath both collar bones, causing fatal massive bleeding.

Some observers who watched videos of the assassination on social media and television noted a lack of attention in the open space behind Abe as he spoke.

A former Kyoto prefectural police investigator, Fumikazu Higuchi, said the footage suggested security was sparse at the event and insufficient for a former prime minister.

“It is necessary to investigate why security allowed Yamagami to freely move and go behind Mr. Abe,” Higuchi told a Nippon TV talk show.

Experts also said Abe was more vulnerable standing on the ground level, instead of atop a campaign vehicle, which reportedly could not be arranged because his visit to Nara was hastily planned the day before.

In videos circulating on social media, the attacker, identified as Tetsuya Yamagami, 41, can be seen with the homemade gun hanging from his shoulder, standing only a few metres behind Abe across a busy street, and continuously glancing around.

?A few minutes after Abe stood at the podium and started his speech — as a local party candidate and their supporters stood and waved to the crowd — Yamagami can be seen firing the first shot, which issued a cloud of smoke, but the projectile apparently missed Abe.

As Abe turned to see where the noise came from, a second shot went off. That shot apparently hit Abe's left arm, missing a bulletproof briefcase raised by a security guard who stood behind the former leader.

Abe fell to the ground, with his left arm tucked in as if to cover his chest. Campaign organizers shouted through loudspeakers asking for medical experts to provide first-aid to Abe, whose heart and breathing had stopped by the time he was airlifted to a hospital where he later pronounced dead.

According to the Asahi newspaper, Yamagami was a contract worker at a warehouse in Kyoto where he was a forklift operator and known as a quiet person who did not mingle with his colleagues.?

A next-door neighbour at his apartment told Asahi he never met Yamagami, though he recalled hearing noises like a saw being used several times late at night over the past month.

Chinese leader Xi Jinping, who early on had a frosty relationship with Abe, sent a condolence message to Japanese Prime Minister Fumio Kishida on Saturday, a day after most other world leaders issued their statements.

?Xi credited Abe with making efforts to improve China-Japan relations and said he and Abe had reached an important understanding on building better ties, according to a statement posted on China's Foreign Ministry website.?

He also told Kishida he is willing to work with him to continue to develop neighbourly and cooperative relations.

Even though he was out of office, Abe was still highly influential in the governing Liberal Democratic Party and headed its largest faction, but his ultra-nationalist views made him a divisive figure to many.

When he resigned as prime minister, Abe blamed a recurrence of the ulcerative colitis he'd had since he was a teenager. He said then it was difficult to leave many of his goals unfinished, especially his failure to resolve the issue of Japanese abducted years ago by North Korea, a territorial dispute with Russia, and a revision of Japan's war-renouncing constitution.

That ultra-nationalism riled the Koreas and China, and his push to create what he saw as a more normal defense posture angered many Japanese. Abe failed to achieve his cherished goal of formally rewriting the U.S.-drafted pacifist constitution because of poor public support.

Loyalists said his legacy was a stronger U.S.-Japan relationship that was meant to bolster Japan's defense capability. But Abe made enemies by forcing his defense goals and other contentious issues through parliament, despite strong public opposition.

Abe was groomed to follow in the footsteps of his grandfather, former Prime Minister Nobusuke Kishi.?

His political rhetoric often focused on making Japan a “normal” and “beautiful” nation with a stronger military and bigger role in international affairs.

Japan is particularly known for its strict gun laws. With a population of 125 million, it had only 10 gun-related criminal cases last year, resulting in one death and four injuries, according to police.?

Eight of those cases were gang-related. Tokyo had no gun incidents, injuries or deaths in the same year, although 61 guns were seized.

Abe was proud of his work to strengthen Japan's security alliance with the U.S. and shepherding the first visit by a serving U.S. president, Barack Obama, to the atom-bombed city of Hiroshima.?

He also helped Tokyo gain the right to host the 2020 Olympics by pledging that a disaster at the Fukushima nuclear plant was “under control” when it was not.

He became Japan's youngest prime minister in 2006, at age 52, but his overly nationalistic first stint abruptly ended a year later, also because of his health.

The end of Abe's scandal-laden first stint as prime minister was the beginning of six years of annual leadership change, remembered as an era of “revolving door” politics that lacked stability.

?When he returned to office in 2012, Abe vowed to revitalise the nation and get its economy out of its deflationary doldrums with his “Abenomics” formula, which combines fiscal stimulus, monetary easing and structural reforms.

He won six national elections and built a rock-solid grip on power, bolstering Japan's defense role and capability and its security alliance with the U.S.?

He also stepped up patriotic education at schools and raised Japan's international profile.?