A three-year-old girl is believed to have witnessed a terrifying attack in which three men were killed and two women badly hurt at a suburban house.

The toddler was found unscathed moments after two gunmen fled from the semi in the commuter town of Bishop's Stortford, Essex, on Tuesday evening.

Local residents identified two of the victims as Keith Cowell, 52, and his son Matthew, 17.

Police have not yet named the third victim, a 33-year-old man, but said the attack in Plaw Hatch Close was "targeted".

Two women, aged 23 and 54, were taken to hospital with serious injuries.

"This is one of the largest scale incidents we've ever seen involving firearms," said Gary Sanderson, of East of England Ambulance Services. "It's totally amazing. We were shocked."

A massive police operation, including a helicopter search, began after neighbours reported a series of bangs at around 9.30pm on Tuesday.

The two suspected gunmen were seen speeding off in a small red car towards the M11.

Rich Guy, 19, who lives just yards away from the scene, said: "I heard a big bang, then a car reversing, driving away with its tyres screeching.

"I didn't think twice though because you sometimes hear driving like that here. It's been a shock, you hear about this more and more these days, it's ridiculous."

The suspects were described as Asians of slim to medium build in their late teens or early 20s.

Speaking at the scene, Chief Superintendent Al Thomas, of Hertfordshire Police, said: "Early information suggests this was a targeted incident and not a random attack."

Tributes left at the scene made reference to Keith and Matt. One message - written on a rugby ball - read: "To Matty. Great mate lost forever. Never be forgotten. Rest in Peace."

The triple murder has rocked the usually quiet neighbourhood of Plaw Hatch Close.

Peter McCaughey, whose house backs onto the three-bedroom semi-detached property where the killings took, said: "I didn't really know the people - they moved in a couple of years ago.

"It's generally a quiet area around this part of Plaw Hatch Close - it's most elderly people who live around here."

Dean O' Connell said: "Plaw Hatch is a really quiet place, we get the occasional bit of trouble, but it's usually very minor stuff, I've lived here for 19 years and I've never seen anything like this before."

He added: "All the residents are in complete and utter shock, you expect this sort of thing to happen in central London, but not down the road where you live.

"I m now concerned about my safety, and the safety of everyone else in the road, there's a children's primary school just down the road, and if it had happened at a different time, children could have been involved, it's just scary."