The half-brother of North Korean leader Kim Jong Un was assassinated at an airport in Kuala Lumpur, telling medical workers before he died en route to a hospital that he had been attacked with a chemical spray, a Malaysian official said Tuesday.

Kim Jong Nam, 46, was attacked Monday in the shopping concourse at the airport and had not gone through immigration yet for his flight to Macau, said the senior government official, who spoke on condition of anonymity because the case involves sensitive diplomacy.

He was taken to the airport clinic and then died on the way to the hospital.

Kim Jong Nam was estranged from his younger brother, the North Korean leader. He had been tipped by outsiders to succeed their dictator father, but reportedly fell out of favor when he was caught trying to enter Japan on a false passport in 2001, saying he wanted to visit Tokyo Disneyland.

He was believed to have been living recently in Macau, Singapore and Malaysia.

Multiple South Korean media reports, citing unnamed sources, said Kim Jong Nam was killed at the airport by two women. TV Chosun, citing unidentified “multiple government sources,” said the women were believed to be North Korean agents. It said they fled in a taxi and were being sought by Malaysian police.

In Washington, the State Department said it was aware of reports of Kim Jong Nam’s death but declined to comment, referring questions to Malaysian authorities.

Kim Jong Nam and Kim Jong Un have the same father, late dictator Kim Jong Il, but different mothers.

Since taking power in late 2011, Kim Jong Un has executed or purged a slew of high-level government officials in what the South Korean government has described as a “reign of terror.” The most spectacular among them was the 2013 execution by anti-aircraft fire of his uncle, Jang Song Thaek, once considered the country’s second most powerful man, for what the North alleged was treason.

South Korea’s government has said North Korea also executed a vice premier for education in 2016 for unspecified anti-revolutionary and factional acts, and a defense minister in 2015 for complaining and sleeping during a meeting.

North Korea also has a history of dispatching spies to kill high-level defectors critical of its system.

In 1997, a nephew of one of Kim Jong Il’s former wives was killed outside a Seoul apartment 15 years after she defected to South Korea. Officials never caught the assailants but believe they were North Korean agents.

In 2010, South Korea arrested what it called a pair of North Korean spies ordered to kill Hwang Jang Yop, a high-level defector who once mentored Kim Jong Il. North Korea denied the allegation.

Mark Tokola, vice president at the Korea Economic Institute in Washington, said it would be surprising if Kim Jong Nam was not killed on the orders of his brother, given that North Korean agents have reportedly tried to assassinate Kim Jong Nam in the past.

“It seems probable that the motivation for the murder was a continuing sense of paranoia on the part of Kim Jong Un, which may be a well-placed paranoia,” Tokola wrote in a commentary Tuesday. Although there was scant evidence that Kim Jong Nam was plotting against the North Korean leader, he provided an alternative for North Koreans who would want to depose his brother.

Tokola, who served as deputy chief of mission at the U.S. Embassy in Seoul, said Kim Jong Nam has been fairly quiet in his exile, but was quoted in the Japanese media in 2010 as saying he opposed dynastic succession in North Korea.

About a year later in December 2011, his father died and Kim Jong Un took power.

(AP)