Video: Meet Ace, the elite protection dog that could 'absolutely kill a man'
Meet Ace the elite protection dog - who can jump through second-storey windows to take down armed intruders.
The three-year-old American pit bull can even recognise a variety of weapons, including handguns and knives, and could 'easily kill a man' if commanded to.
He is the top dog at Dark Dynasty K9s - who specialise in training elite protection dogs for the police, celebrities and billionaire clients around the world.
Owner Marlon Grennan, 28, said: "If he wasn't under control, he could absolutely kill a person.
"Ace is one of the most muscular pit bulls in the world right now. He is absolutely a super dog; a one in a million."
It takes years of dedicated training for a dog to reach this level and Marlon has been training Ace five times a week for the last three years.
He is also fed a protein-rich diet and is kept in an almost constant exercise regime to maintain his muscular physique.
Training began when Ace was just five months old when Marlon recognised his natural drive and strong nerve.
He begins by removing them from the main group so they can train alone - as mixing with other dogs can disrupt their training regime and make them dangerous.
Marlon said: "You don’t want any other dog trying to dominate them. When you are building a protection dog they literally have to have the biggest ego ever.
"You want him to think he is literally unstoppable at every turn. So, this dog will never see any failure."
The latest recruits to go through the elite training school are puppies Hercules and Dynasty, who were sired by Marlon's most famous dog, Hulk, the 175lb pit bull, who made headlines around the world this year.
"When we first look at the puppies we look for something called a basic prey drive. It's basically the dog’s want to chase a ball, for example," said Marlon, who lives in New Hampshire, USA.
"We put so much time picking the perfect dog and selecting ones that are balanced. We need the best, ones that are not just gonna go awol one day.
"I hope to get at least three working dogs out of a litter. Sometimes you can get five, sometimes you get one and sometimes you get none - that's just the way the cookie crumbles with this kind of work."
Ace, who weighs around 85lb, also started his career this way before being trained to jump into cars, run along narrow walkways recognise weapons in a business-type situation and take down would-be assailants with bites and brute strength.
However, just a handful of dogs have what it takes to make it to this level.
Marlon added: "Sometimes you get to a point when you start to put heavier pressure on a dog and they shutdown.
"It's an important part of being a trainer to recognise this and pull the plug on the dog's training.
"You then need to get them back to regular socialising and find a way to reintegrate them into being regular family dogs.
"The problem a lot of people have is they go too far and they don't know when to pull the plug.
"Then suddenly, boom, one day there is an explosion in the dog and they start biting or something else goes wrong.
"This work is very detailed. You need to be paying attention at all times."
American pit bull terriers lineage can be traced back to the UK where they were typically involved in bloodsports such as bear baiting and bull baiting.
The breed is one the four dog breeds that have been banned in the UK.