Until at least 2002, Howlett belonged to a criminal group known as the Glenorchy Mafia, with his brother Shaune Henry Howlett, Benjamin Maxwell Pearce, and Gavin Raymond McIntosh. In 2002, Howlett was sentenced to 6 months imprisonment for instigating an aggravated assault on rival gang members Steven Maxwell and Brett Hynes. Howlett was later involved in an attempt to blow up a forensic laboratory. On 8 March 2000, Howlett, a criminal associate named Scott Raymond Dale, and Joseph Andrew Tonner, went to the Government Analytical & Forensic Laboratory with an explosive device and two tins of petrol. The three climbed onto the roof of the administration building. Howlett prised open a window, and Tonner placed the explosive device on shelving in the building and lit it. The purpose of doing so was said by the prosecution to be to destroy evidence believed to be in the Laboratory, that would lead to the conviction of Graeme Hall for trafficking in a substantial quantity of amphetamine. On 22 November 2004, Howlett pleaded guilty to possessing a dangerous object with the intent to commit a crime, and attempting to unlawfully injure property, possessing an explosive device between January 1999 and March 2000, and to igniting petroleum and a bomb in an attempt to damage material inside a forensic laboratory. Howlett received 2 years' imprisonment with 20 months suspended, with Justice Peter Underwood noting, “I have not heard such convincing evidence of self-motivated rehabilitation by a prison inmate”. On 24 March 2010, Howlett pleaded guilty to trafficking in methylamphetamine, after a "sting" operation saw him exchange 27.1 grams of the drug and $4,100 for five pistols. Howlett received 2 years’ imprisonment for this crime. On 24 June 2018 Howlett took a taxi to the corner of Liverpool Street and Harrington Street, and walked a short distance to Pablos cocktail bar whilst his face was smeared with red war-paint, and armed with a 7.2 x 39 mm calibre self-loading rifle, fitted with a bayonet. Attached to the weapon was a magazine, which contained at least 25 cartridges. He was also in possession of 143 rounds of spare ammunition for the weapon. He fired 25 bullets in quick succession into and towards the entrance door. The bullets, fired from an ex-military semi-automatic rifle, tore through the club's steel-clad door. At his sentencing hearing, Howlett's lawyer Greg Richardson argued that he was under the influence of drugs, saying "This is so bizarre, so out of the range of things you would expect him to do... that alone would suggest that there is some kind of trigger, which is clearly explained by drugs." Howlett received 5 years imprisonment without parole for 3 years for the shooting.
Powerlifting
Howlett is a noted Tasmanian powerlifter. Howlett placed 1st at World Raw Powerlifting Federation Tasmanian State Titles in 2005, 2012, 2013, 2014, 1st at World Championships in 2012, 2nd at World Raw Powerlifting Federation World Championships in 2013, 2nd at Russian Open Championships in 2015, and 1st in the Down Under Classic in 2017.
