By Jon Kay
BBC News, Phoenix
Two serial killers have been bringing such fear to the streets of Phoenix in the US that residents are taking steps to arm themselves.
Linda O'Neill's hands are shaking as she aims her brand new gun at the target.
She shoots. She misses. It is hardly surprising. At the age of 41, she has never owned a weapon before - in fact she has never even touched a gun - but this week she spent more than $500 (£270) on a Glock 9mm pistol.
"I just had to get something to protect myself," she says.
The 'Baseline Killer' - police do not know if this photo-fit is accurate
Linda is one of hundreds of people in the US desert city of Phoenix who have decided to arm themselves after weeks of terrifying news headlines about two serial killers.
Local people believe the two are competing with one another, to try to kill the most victims in this usually peaceful city.
"I'm a wreck," says Linda.
"It's terrifying. I won't go out at night. No way.
"Some of my friends used to work in the evenings, but now they've given up their jobs. They're too scared to be out after dark. They'd rather be safe at home - even if they're not earning money."
The attacks started last August, but it has taken several months for the police to realise that there seem to be two separate assailants on the loose.
The first is known as the Baseline Killer - named after the neighbourhood where he committed his first murder.
Since that attack, he is believed to have killed at least another five people, as well as raping and kidnapping 20 more.
The police have issued a photo-fit of a black man with dreadlocks, but they admit they do not know how accurate the picture is. The assailant wears many different disguises.
The second man is known as the Serial Shooter.
He is believed to be operating entirely separately from the Baseline Killer - shooting human beings and animals randomly from his vehicle. He has taken the lives of at least five people.
Most local people believe the two killers are involved in a deadly game of one-upmanship. When one strikes, the other follows.
"The sooner they are caught, the better it is for this whole city," says Justin Schneider, wearing a red beret as he patrols the park. The 21-year-old is a Guardian Angel - one of 30 volunteers now trying to restore calm on the streets of Phoenix.
Even at night the temperature exceeds 38C (100F) here, but Mr Schneider and his colleagues are undeterred.
They sweat in the heat as they search a local petrol station where a woman was murdered last week.
"You can't have two guys on the loose, seeing who can kill the most innocent people," Mr Schneider says.
"There's so much bad stuff going on right now. I just want to do something to make this neighbourhood feel better."
At this time of year, the shopping malls and cinemas are usually busy in the evening, as people take advantage of free air-conditioning - but this summer things are different.
Restaurants are empty - in fact much of the city falls silent once the sun has set.
"I'd rather be sweatin' hot in my home than out on the streets being shot at!" remarks one passer-by.
Phoenix police are appealing for calm.
"Every community goes through crises," says Sergeant Andy Hill, "and we'll get through this crisis."
The Baseline Road has been the scene of a number of killings
He acknowledges there has been criticism in some communities, but he defends his officers for not making more progress.
"No, we haven't found these killers yet, but it's not for the lack of trying. We are doing everything possible - but there isn't much to go on," he says.
"You have to remember, we don't even have a description of the Serial Shooter at this stage."
The police will not say categorically that the two men (and it's not certain they are both men) are competing with one another, but in the city's multi-ethnic neighbourhoods there is little doubt that this is a contest.
There are now more than 120 officers working on the hunt for the two murderers - and police are offering a reward of $100,000 (£54,000) - but, as thunder and lightning crackle over the empty streets of Phoenix, it seems nobody knows who these serial killers are. And they may not even know one another.
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