South Korea has a relatively high level of public safety, to the degree that few feel uneasy about riding a subway train in the late hours. But this should not let authorities and the public loosen their vigilance against possible terrorist attacks or other threats to society.

In fact, string of recent cases has raised questions about the nation’s ability to deal with terrorism and threats to public safety ― a teenager joined the Islamic State militant group and two men went on separate shooting sprees with their hunting guns.

Then came the knife attack on U.S. Ambassador Mark Lippert, the first-ever life-threatening assault against the top American diplomat here.

Most of all, the incident showed how complacent relevant authorities, not least the Korean security agencies and the U.S. Embassy, were about the safety of the top diplomat from a country which has many enemies.

It is more regrettable that Lippert was ― as he often proclaimed ― a man who wants to be a “friend in the streets” of the Korean people. The envoy should have been given “invisible, yet proper” protection as he was reaching out to the Korean public.

One more thing we need to learn from the attack on the U.S. envoy is that terrorism does not necessarily require massive mobilization, an extensive network or sophisticated preparation.

Lippert’s sole attacker, Kim Ki-jong, seems to be a social outsider and a typical leftist radical who hates the U.S. and follows the anachronistic socialist regime in North Korea. He threw a piece of concrete at the Japanese ambassador in 2010.

There could be many such potential terrorists in the country because this society has a considerable number of radicals and fanatics who are stuck on the extreme ends of the ideological spectrum and social outcasts like the 18-year-old high school dropout who joined the IS.

These two groups ― radicals like former leftist lawmaker Lee Seok-ki, who was convicted of instigating an armed rebellion, and “lone wolves” who are bent on venting their anger at society by violent means ― could pose security threats to the society.

Moreover, we in the South live with persistent security threats from North Korea. It is still disturbing to recall the long list of terrorist acts perpetrated by the Pyongyang regime: the 1983 bombing of the entourage of President Chun Doo-hwan, the 1986 bomb blast at Gimpo International Airport, the 1987 bombing of a Korean Air jetliner and the 1997 assassination of a relative of Kim Jong-il who defected to the South.

All these call upon us to make a comprehensive review of our antiterrorism posture and make our security system as tight as possible. One of the first steps should be the legislation of an antiterrorism act like the Homeland Security Act of the U.S enacted in the aftermath of the Sept. 11 attacks.

The Lippert case should provide momentum for the National Assembly to restart discussions on the issue. How can we cope with terrorist attacks on a larger scale if we are unable to protect the U.S. envoy from an extremist who previously attacked another diplomat and stop a misguided teenager from joining a terrorist group in the Middle East?