<sod >'The child from the pram was dragged 100m down Bourke St with the car,' a witness said, adding the child looked around 'three or four years old'. Police have arrested a man wearing nothing but red underwear at the Elizabeth St end of the mall.< eod>< sod > 'The child from the pram was dragged 100m down Bourke St with the car,' a witness said, adding the child looked around 'three or four years old'.  'People were running out of the way, they were going very very fast,' another witness, Rebecca Russo, told The Age.  'I saw him hit a few people. I saw bodies flying into the air.' Ambulance Victoria confirmed a number of people have been injured  One witness said they performed CPR on a man injured during the carnage Police said the situation had been contained, but have requested that people avoid the area Other people said they heard a boom and gunshots, with one man telling Sky News there was 'a hell of a lot of blood'. The same witness also claimed he saw the car hit a pram.  'There's someone on the middle of the ground and there's blood all over the street,' Rishi Hathiramani, a CBD shopkeeper, told AAP. 'I've seen accidents but never this bad. 'It's pretty brutal.' A number of CBD businesses are in lockdown, while others have been evacuated. 'A heap of people ran into my store, it was horrible. Half of my staff are in tears,' a Strandbags manager told AAP.< eod>