A child is dead and a politician made a joke about what led to it.

Liberal Democrat Senator David Leyonhjelm has been widely criticised on Twitter for writing an “insensitive” tweet about the Bourke St incident on Friday afternoon.

As early news broke that a car ploughed into pedestrians on Melbourne’s Bourke Street, Leyonhjelm tweeted, “Probably one of those semi-automatic assault cars.”

Leyonhjelm, a well-known pro-gun Senator from New South Wales, was perceived as trying to make a point about the idea that it is people who commit crimes and not objects.

Users were quick to blast the politician for being “opportunistic” enough to try to make a political point at a time of such tragedy.

Talking to AAP, Leyonhjelm said the outrage “only emanates from those who are too stupid to get it”.

“My comment referred to the ‘rogue’ car, as if the driver is irrelevant,” he told AAP. “It’s people who commit crimes, not inanimate objects. The same argument applies in the debate about firearms.”

Since he pushed send on Friday afternoon, police revealed three people were killed and up to 20 more were injured in the incident.

Leyonhjelm’s tweet has since attracted more than 1,000 replies.

“I’m sure the families of the people who died today appreciate your wit,” one user immediately replied.

Sportswriter Richard Hinds was as similarly swift in tweeting his disbelief at Leyonhjelm’s comments.

“There is opportunism and then there is psychosis. An awful line crossed here by an elected official. Utterly shameful,” he wrote.

Meanwhile, in a since deleted tweet, actor Rhys Muldoon tweeted, “a child was killed and you’re scoring pathetic political points. You are a disgraceful man. Leave public life. Now.”

He followed up his criticism with another, writing “I’ve just realised my attack on the disgraceful @DavidLeyonhjelm is also a political attack, therefore I’m deleting. I stand by sentiment.”

At this stage, three are confirmed dead and 20 more injured in the Bourke Street carnage. One of those dead has been confirmed by the Herald Sun to be a young child.

Four of those injured are believed to be children who are being treated at the Royal Children’s Hospital, with one in a critical state.