Coleman was caught after undercover officers from MI5 engaged with him in encrypted chat as he sought to buy weapons. In early September 2023, he arranged to buy a Skorpion automatic weapon, an AK47 rifle and bullets in France to target a local mosque, but abandoned the plan. On September 29, 2023, he arranged with an undercover officer to buy a Makarov pistol, five magazines, and 200 rounds of ammunition, and was arrested in a Morrisons car park in Stratford, east London. He dropped £3,500 in a Land Rover Discovery and picked up a holdall containing the handgun and ammunition.
At his home, police found Nazi paraphernalia including a rock with a Swastika, a Black Sun flag, extreme right-wing books, a stash of knives, an air rifle, and a device to detect bugs and cameras. He idolized Thomas Mair, the extremist who killed MP Jo Cox, and had emailed the far-right white supremacist organisation Patriotic Alternative in July 2021. He started viewing extreme right-wing material at age 14.
He also had plans for potential terrorist attacks such as hijacking a plane, targeting the home of the Lord Mayor of London, and using explosives in a cash machine, knives, and crossbows. He compiled a hate list of colleagues and customers he branded with racial slurs or as 'race traitors'. Coleman was a former part-time Tesco worker. The specific mosque in France has not been disclosed, and Coleman is awaiting sentencing.