By commanding an unauthorised attack on Tanzania in October 1978, Butabika was responsible for the outbreak of the Uganda–Tanzania War which ultimately resulted in his death in combat, probably during or shortly before the Fall of Kampala.

The initial plan was to blow up Obote's plane at the Entebbe International Airport on 24 January 1971, but Butabika's wife informed her brother-in-law Ahmad Oduka, Senior Superintendent of Police, of the plot.

[13] Soon after the coup, Butabika was involved in the kidnapping and murder of two United States citizens around July 1971, namely journalist Nicholas Stroh and Makerere University lecturer Robert Siedle.

[19] According to George Ivan Smith, Butabika believed himself to be a "demi-god" as the government allowed him to kill and torture at will,[5] while Peter Jeremy Allen described him as "merciless psychopathic killer" of "low mentality".

[6] Similarly, businessman Gordon Wavamunno had a very negative opinion of Butabika, and regarded him as one of those who "were intoxicated with unlimited and irresponsible power, and did not hesitate to abuse it at the slightest opportunity or excuse.

[10] According to Amnesty International, the tribunals Butabika chaired were de facto kangaroo courts and passed judgements without regard to laws or proper procedure.

[6] One Ugandan dissident noted that the Lieutenant Colonel's tribunals generally resulted in the death of the accused; they were either executed or released, only to be rounded up and murdered by Uganda's secret service, the State Research Bureau.

[7] Butabika chaired several prominent tribunals, such as when he sentenced British author Denis Hills to death in 1975 on charges of sedition for calling Amin a "black Nero" and a "village tyrant".

[15][30] Two years later, he chaired the tribunal that sentenced 12 men to death for conspiring to murder Amin during a coup attempt code-named "Operation Mafuta Mingi";[31] this trial in particular was described as "travesty of justice, a 'show', since the conventions and pleas of guilt were obtained by force from the accused".

One of Amin's close advisors, Colonel Abdu Kisuule, later claimed that the entire incident had been orchestrated by Butabika to gain "favors and cheap popularity" from the president.

[18][23] Others however report that the exact identity of the Ugandan soldier remains unknown, and that Butabika was lied to by his subordinates about the course of events; in that case, it is possible that he actually believed that Tanzanian border guards had initiated hostilities.

[22][1] His forces easily overran the Tanzanian troops stationed at Mutukula and Minziro, whereupon he telephoned Amin, claiming that Tanzania had launched an attack and that he had responded with a counter-attack.

[8][2] By the time the Ugandan border town Mutukula fell to the Tanzanian army in January 1979, Butabika was back in Kampala and prepared the celebrations for the 8th anniversary of Amin's rule.