He was armed with a civilian version of a SIG SG 550 assault rifle, a pump-action shotgun, two handguns, a homemade bomb and had entered the building disguised as a police officer.

Leibacher had a long history of criminal actions, among them several instances of assault, illegal importation of guns and child molestation, as well as violent threats.

[1][2] In 2001, around 500,000 people in Switzerland possessed firearms as a result of the Swiss Militia System, which requires men over 20 to be ready for a call to service.

[7][8] His father said when he started school it was as if "Satan entered him"; he was first arrested at 13 for publicly shooting a rifle and threatening to kill his own mother.

His studies only lasted for a semester, as he was arrested for smuggling watches in Turkey and spent a resulting seven months in prison.

[15] After his release, he became a management consultant and owned a company, Media Zeitschriften AG, which he used for illegitimate financial purposes.

[8] Throughout the next two decades he was accused of a variety of criminal acts, among them illegal importation of handguns into Switzerland,[11][16] for which he was convicted three times but only got warning sentences.

[9] He was diagnosed by doctors in 1996 with antisocial personality disorder, probable alcoholism, mental impairment and mild schizophrenia.

[21][11] Trying to end the legal battle the Director of Transport Robert Bisig [de] offered to meet with Leibacher.

[19] In the final months before the shooting, Leibacher closed his bank accounts, sold his home and his shares in stocks.

The day before the shooting, he instructed a Swiss funeral home that when he died, he was to be cremated and have his ashes scattered across the Atlantic.

The day of the attack he sent his lawyer a key, which unlocked a locker that contained several folders of case information.

[25][24] Despite making some preparations for escape, such as renting a motor scooter, evidence suggests he intended to die in the attack.

This letter was written in poor English, and read in part:[19] I am persecuted by the Swiss government for some critics [...] If these things are driving out of control, it is because I am completely tired to fight against that supremacy.

I am forced to do the same as they doOn 27 September 2001, at 10:30 a.m.,[24] Leibacher arrived at the canton's parliament building (German: Parlamentsgebäude) armed with four firearms (SIG SG 550 assault rifle, Remington Model 870 Express shotgun, Smith & Wesson Model 19-7 revolver, SIG Sauer P232 pistol)[26] and dressed in a homemade police vest.

[2][10] Leibacher left a suicide note in his car (of which he made 29 copies) titled "Tag des Zornes für die Zuger Mafia" ("transl.

[28][11][10] It contained various allegations against the authorities of the canton, denouncing them as a "Mafia judiciary" that had victimized him through "illegal and criminal means".

At 4 p.m., Tino Jorio [de], who remained uninjured, organized an eleven-member task force, which met under his leadership at 8 a.m. the following morning.

[33] Bisig and Schwerzmann, together with the executive secretaries, took over the management of the orphaned departments, and parliamentary business was suspended until the end of November.

On 23 October, the government met for the first time in its new form, and on 29 November, the Cantonal Council also resumed its work, now in the large hall of the Zug police building.

[33] Swiss president Moritz Leuenberger ordered the national flag to be flown at half-mast for three days after the incident.

[34] The mayor of Zug, Christoph Luchsinger, described the aftermath as "a terrible scene of horror" and the shooting as an "attack on our democracy".

[10] On 1 October, the official funeral service for the victims was held in the Zug parish church of St Michael's [de].

[41] During the ten years until his retirement in September 2011, Timo Jorio and his wife Ruth, as well as Landesweibel, accompanied the relatives of those killed and arranged for lawyers to help with legal issues.

[44] In 2004, during a National League ice hockey game between EV Zug and SC Bern at a stadium in St. Gallen, fans of Bern taunted and provoked Zug supporters by displaying a large banner celebrating the massacre, adorned with a skull and crossbones alongside the text "Danke Leibacher" (transl.

[20] The shooting also led to a change in how people perceived as hostile or uttering threats were handled by several cantons.

The public prosecution office now assigns a case manager to such people to assess the violence risk by gathering all known information, and such individuals are tracked in databases.

[37] There was no large societal campaign for stricter gun laws, as seen in other countries that had experienced similarly deadly attacks (e.g. the United Kingdom after the Dunblane massacre).

The proposed policies included the ban of the sale of fully automatic weapons and pump-action rifles, and that military-issued firearms must be held in army depots.

[4][53] The idea of changing the free access to buildings resulted in criticism, as some believed this would damage the transparency between politicians and the public.