Two girls aged six and seven have died after a car drove into a group of people in Handsworth, Birmingham.
The children were taken to hospital following the collision in which four other people were also injured, but later died of their injuries.
A 12-year-old girl and a 13-year-old boy are being treated for serious injuries, which are not believed to be life threatening. A 39-year-old woman remains in a critical condition after also being hit by the vehicle.
"I was horrified by what I saw," one anonymous witness told the Daily Mail. "The car must have been doing 100mph. I pray they pull through. There were bodies everywhere."
West Midlands Police have arrested a 34-year-old man on suspicion of dangerous driving. He currently remains in custody for questioning.
Sergeant Steve Newbury, from the force's Collision Investigation Unit, said: "We still continue to investigate the circumstances around this tragic incident and officers continue to liaise with the family of those involved.
"I am appealing for witnesses to come forward in particular I want passengers who were travelling on the number 101 bus at around noon along Grove Lane towards Oxhill road to call me or one of my team."