Video report by ITV News Correspondent Olivia Kinsley
Police are seeking a second man in connection to a car crash which left three teenage pedestrians dead in west London.
A 28-year-old man has already been arrested on suspicion of dangerous driving.
The three boys who died are thought to have been on their way to a 16th birthday party together with friends in Hayes when they were struck by a black Audi which mounted the pavement.
Emergency services were called but all three were pronounced dead at the scene.
Police said two of the boys were aged 16 and a third was 17 years old.
They have been named locally and in floral tributes as George Wilkinson, Josh Kennedy and Harry Rice.
Police said the car involved is "believed to have been travelling at high speed".
At least two men left the vehicle after the crash, at 8.40pm on Friday night, the Metropolitan Police said.
One of them, a 28-year-old man, was detained by a member of the public and was later arrested on suspicion of dangerous driving.
He was taken to a west London hospital for treatment and was then transferred to a north London police station for questioning.
On Saturday evening, police announced they are now seeking a second man in relation to the crash, and have not ruled out that there could have been more passengers in the car.
Family members came to lay flowers at the site of the crash on Saturday morning.
The mother of one of the victims left a card to "my darling baby boi" which said "My heart is broken".
Another said "To my bro. Always together forever."
A large crowd of young people gathered at the scene of the crash on Saturday afternoon to leave tributes and release balloons.
A number of other teenagers standing with the group at the bus stop at the time of the incident were unharmed in the crash.
Tony Kitchin, 44, who works as security guard at a haulage firm nearby, said the road was a "speed trap".
"I'm really surprised we haven't had more horrific accidents like this," he said.
"No parent should have to deal with that. My heartfelt sympathies go out to the family and friends of the people who lost their lives last night."
Police have made an urgent appeal for witnesses.
DS Jane Shaw, of theMet's Serious Collision Investigation Unit, said: "These are horrific circumstances that have resulted in three young people on a night out losing their lives.
"Dedicated family liason officers have been put in place to support the next-of-kin of the victims.
"Our thoughts are with them.
"We know that there was a large party nearby and many people would have been travelling through the area and saw what happened or witnessed the aftermath. I need these witnesses to contact police immediately.
"We are also particularly keen to trace other motorists travelling through the area at the time."
Anyone with information is asked to call the Met's road policing team on 0208 991 9555 or contact Crimestoppers anonymously on 0800 555 111.