A two-year-old girl is in a critical condition in hospital after she was hit by a moped in west London.
The toddler was crossing the road with her family at traffic lights when the collision happened in The Vale, Acton about 6.30pm.
The 19-year-old rider of the moped stopped at the scene. He was arrested on suspicion of dangerous driving and driving while under the influence of drugs. He remains in custody.
Residents heard the mother’s screams as she crouched over her daughter in the road with her older son holding her hand.
One woman, who witnessed the aftermath, said: “I heard the mother screaming and people began rushing out their houses and from the bus stop.
“She was a blonde haired little girl and she was lying on the ground while her brother and her mother were kneeling around her.
“Her eyes were closed and she was losing consciousness. There were shopping bags on the floor and a toy in the road.
“The mum was on the phone to the ambulance service saying ‘help she has been knocked over,’ while the brother was trying to comfort her.
“They were all distraught, it was absolute mayhem.”
A doctor on a bicycle and a nurse driving past in her car spotted the incident and scrambled to help before emergency services arrived, the witness said.
“The doctor jumped off his bike and took control of the situation,” the woman added. “He asked people to run to the nearest supermarket to get an emergency defibrillator and then the emergency services arrived.”
Witnesses described seeing five police cars, one police van, five ambulance vehicles and a helicopter at the junction which was closed off following the incident.
The Met said the injured child is in a critical condition.
DS Nush Puvitharan from the Serious Collision Investigation Unit said: “The incident happened as the girl and her family were crossing the street at traffic lights while other vehicles waited.
“Some of those road users would have seen the incident, or may have recorded the events on dash-cam footage and, if so, I would urge them to come forward and speak to police.
“This information could prove vital in ensuring we can piece together exactly what happened in this incident.”
Officers are urging witnesses to contact them on 020 8246 9820 or 101, quoting CAD6736/8June.