For now, Mr Khan’s campaign truck has become a crime scene, cordoned off and guarded by commandos as forensic experts comb the area.
Overnight, thousands of Mr Khan’s supporters gathered for a peek, many waving party banners.
Information Minister Marriyum Aurangzeb said on Thursday the attacker had been taken into custody, and shared an apparent confession video that was circulating online.
“I did it because (Khan) was misleading the public,” said a dishevelled man in the video, shown with his hands tied behind his back in what appears to be a police station.
He adds that he was angry with the procession for making a racket during the call to prayer that summons Muslims to the mosque five times a day.
Pervaiz Elahi, the Chief Minister of Punjab, said officers who leaked the video would be disciplined.
Pakistan has been grappling with militancy for decades, and politicians are frequently targeted by assassination attempts.
The attack on Mr Khan had echoes of the 2007 assassination of another former prime minister, Benazir Bhutto, who died when a huge bomb detonated near her vehicle as she greeted supporters in the city of Rawalpindi while standing up through the roof hatch.
Mr Khan was booted from office in April by a no-confidence vote after defections by some of his coalition partners, but he retains huge support in Pakistan.
He was voted into power in 2018 on an anti-corruption platform by an electorate tired of dynastic politics, but his mishandling of the economy – and falling out with a military accused of helping his rise – sealed his fate.
Since then, he has railed against the ruling establishment and Prime Minister Shehbaz Sharif’s government, which he says was imposed on Pakistan by a “conspiracy” involving the United States.
Mr Khan has repeatedly told supporters he was prepared to die for the country, and aides have long warned of unspecified threats made on his life.
The attack drew international condemnation including from the US, which had uneasy relations with Mr Khan when he was in power.
“Violence has no place in politics, and we call on all parties to refrain from violence, harassment and intimidation,” US Secretary of State Antony Blinken said in a statement.