Security complacence enabled would-be Brasília bomber

On Christmas Eve last year, Brazil was put on high alert. A fiercely contested election two months prior saw Luiz Inácio Lula da Silva unseat then-President Jair Bolsonaro — sparking an angry response from the defeated far-right leader’s most radical supporters. Protests around the country saw highways blocked with overt calls for a military coup. And then, on the morning of December 24, military police encountered and disposed of an explosive device left outside Brasília International Airport.

Pro-Bolsonaro journalist Wellington Macedo is one of those accused of planting the bomb, in an attempted terrorist attack which investigations show could have had catastrophic results. The device in question was triggered, but did not detonate.

Authorities had monitored Mr. Macedo for over a year after he was arrested for his involvement in anti-democratic protests in favor of the former president. At the time of the plot in December, he was wearing an electronic ankle bracelet that logs his location in real time. The bracelet’s GPS tracked the route he took to plant the bomb, yet nothing was done to stop him or to track him down in the immediate aftermath.

On the night of December 12, the day of Lula’s certification as president-elect, Mr. Macedo was wearing his ankle bracelet as he took part in public unrest in Brasília, where pro-Bolsonaro groups sought to break into the Federal Police headquarters and torched vehicles on the capital’s streets.

He was forbidden from meeting with anyone without permission from the court, and was banned from having a presence online — two...