In an episode that evokes memories of Cold War era spy sagas, Kim Jong Nam - the half-brother of North Korean dictator Kim Jong-un - appears to have been assassinated on February 13 at Kuala Lumpur's airport in Malaysia.

Reports indicate that two female agents, with probable connections to North Korea's security services, poisoned the estranged sibling with lethal toxins.

Malaysian authorities are also holding a North Korean suspect and have released the names of several North Korean suspects thought to have fled the country after the killing.

Meanwhile, there has been a diplomatic standoff between Kuala Lumpur and Pyongyang with both sides accusing the other of interference in the investigation.

Game-changer: Nerve agent

There are a host of potential reasons why Kim Jong-un wanted to eliminate his seemingly harmless brother - but the most probable was his paranoia and ruthless pursuit of political legitimacy at home.

Kim Jong-nam's murder follows a host of purges over the past few years, including the killing of Kim Jong-un's uncle and top adviser Jang Song-thaek in 2013. The purges also fall in line with his marked up-tick in provocations aimed at enhancing the regime's nuclear and missile capabilities.

This week, the plot has deepened as Malaysian authorities have indicated that Kim Jong-nam appeared to have been killed by the highly lethal VX nerve agent, a substance that is banned as a chemical weapon by the Organisation for the Prohibition of Chemical Weapons (OPCW).

This attack - if confirmed that it was conducted with a VX nerve agent - would be a game-changer. VX is a lethal agent that effectively shuts down your muscle system in a short period and causing muscle clenching, convulsions and eventually death.

Stockpiles of the substance, which used to be held by some states - including the United States and the Soviet Union - for potential military use, have been mostly eliminated as the Chemical Weapons Convention (CWC) bans the agent.

This incident raises a host of questions on how to deal with the incident as the assassination is not only an attack of terrorism but could be an act using WMDs- one of the deepest fears of the international community.

Despite this, North Korea - which is not party to the CWC - maintains as much as 5,000 tonnes of lethal agents including: VX, sarin, mustard, tabun and hydrogen cyanid.

VX nerve agents have never been knowingly used by states during combat, but there have been some cases of non-state actors using them such as an attack by the Japanese cult Aum Shinrikyo in 1994-5 (although different from the sarin gas used in the large scale Tokyo subway attack).

VX agents are not simply lying around research facilitates and are illicit and deadly nerve agents, which North Korea is known to possess - almost eliminating any doubt that this attack was committed by some group outside of one ordered by Pyongyang.

China out?

The North's chemical programme has kind of fallen under the radar in most analysis about the threat perceptions emanating from the North, as most concerns - rightfully so - focus on its conventional forces and nuclear programme.

That said, intelligence communities in the West and South Korea have warned for years about the dangers of the North's chemical and biological weapons programme and their potential use in asymmetric ways should the Kim regime feel threatened.

This incident raises a host of questions on how to deal with the incident as the assassination is not only an attack of terrorism, but could be an act using weapons of mass destruction (WMD) - and the materials may have crossed borders raising serious questions about horizontal WMD proliferation from the North - one of the deepest fears of the international community.

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The risk of proliferation to non-state actors is perhaps the most startling concern, especially as sanctions continue to bite down on the income flows into the North.

Indeed, earlier this month, China's Ministry of Commerce and Customs Administration made a highly visible joint announcement that it would "ban" coal imports from North Korea, effectively immediately, for the rest of this year.

Last year, North Korea exported 22 million metric tonnes of coal to China, netting nearly $1.2bn in cash for the Kim regime. Beijing is - by far - the North's largest export market for coal, and Pyongyang depends on China as a trading lifeline, with nearly 90 percent of trade going through Beijing.

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Despite the concerns on ratcheting up the pressure on North Korea, some integral international norms and laws - such as the moratorium on the use of chemical weapons - should be adhered to.

Malaysia, a state that has traditionally had good ties with the North, should move to sever diplomatic ties with Pyongyang if it is sufficiently proved that there is a link between the killing and state security organs.

Meanwhile, the Trump administration in the US faces tough options as it reviews its North Korea policy - but it must look at taking immediate steps such as moving towards reinstating Pyongyang on the list of state sponsors of terrorism.

J Berkshire Miller is the director of the Council on International Policy and is a fellow on East Asia for the EastWest Institute.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.