An astonishing 40 people were shot in Chicago on the first full day and night of the three-day Memorial holiday weekend, with four deaths, including a 15-year-old girl hit by a car driving along Lake Michigan.

There were still two days left for bloodshed in the violence-riddled summer holiday weekend, that saw 12 people killed the previous year. It looks like this year's toll would easily surpass the total number of people shot at last year, which was 43.

Another victim was 27-year-old Garvin Whitmore who was sitting in a car talking to a woman when someone walked up to his window and shot him in the head. The woman picked up another gun in the car to return fire as the shooter ran away, police told the Chicago Tribune.

By mid-Sunday (29 May) no one had been arrested in any of the shootings, according to investigators, who said most of the violence in the city can be attributed to some 1,500 repeat offenders.

"I think people have to realise it's a big city, but it's a beautiful city, and it really is a safe city, it's just — as we've said before — it's about 1,500 people that we know are really driving the violence. Those are the people we're trying to concentrate on," First Deputy Police Superintendent John Escalante told CBS Chicago.

But another cop disagreed, telling the Daily Beast: "Chicago is an ugly city full of violent people."

It's difficult to catch and prosecute the shooters because residents are terrified of them. "The code here is don't talk," said one local. "Not if you wanna live. Not if you wanna live peacefully."

Escalante said the shootings occurred even though the department deployed thousands of additional officers — and would continue to do so — concentrating many of the extra patrols on the city's violent, poverty-stricken West Side, where almost half of the shootings occurred.

"It's a struggle for us, but we will be putting extra resources" there "because they have certainly had an unacceptable level of shootings," said Escalante. "We're asking the men and women of the Chicago Police Department to step up and do their best."

There have already been more than 1,400 shootings and nearly 300 homicides in Chicago in 2016.