The 25cm-long scar looks like a fossilised alien life form snaking the length of Derrick Tan's left inner forearm.
The disfigurement is the result of a vicious mauling six years ago by an aggressive alsatian the then police dog trainer was playing with.
"We were playing a game of Fetch but it suddenly flipped and went at my arm three times. I needed more than 130 stitches. Let me show you something," Mr Tan says excitedly as he swipes his right index finger furiously through the photographs in his iPhone.
He finds the picture he wants. Taken just after the attack, it is a nauseating shot of his mangled arm with the skin ripped open.
Because the dog attacked another trainer a week later, it had to be put to sleep.
Mr Tan was on medical leave and news of the dog's fate rattled him. "I rushed down to the clinic to say goodbye to him," he says, his face clouding over at the memory.
This unguarded display of tenderness is incongruent with his menacing appearance. Pierced, heavily tattooed and with his hair bleached blond, the 33-year-old bachelor is often mistaken for a ruffian.
And he was one actually.
He flunked his studies, joined various gangs, sniffed glue, did drugs, was arrested for rioting and had other unsavoury habits.
But the love of his parents, and his own love for animals, set him straight.
A former dog trainer and para vet with the Singapore Police Force, he is now the operations manager of Sunny Heights, the largest day- care centre for dogs in Singapore.
Animal lovers also know him as the founder of Voices For Animals, an outfit which rehabilitates former breeding dogs and cats and provides pet therapy sessions for the elderly and people with special needs.
Mr Tan, who is three credits away from getting a psychology degree from an Australian university, also works with youth at risk.
Engaging, with the straight-talking manner of someone with no hang-ups about his past, Mr Tan is the elder of two children.
His father used to drive heavy vehicles on construction sites, and his mother sold noodles in a coffee shop.
The family lived in a one-room rental flat in Taman Jurong before moving into their own three-room HDB flat in Bukit Batok.
As a kid, he was often roughed up for standing up to bullies who taunted his sister who suffers from Short Leg Syndrome and walks with a gait.
The brashness also came with a hyperactive disposition which made him more than a handful for his teachers and parents.
"My mother usually left the flat at 4.30am to open her stall but would come back at 6.30am to wake me up for school. I would get dressed, but the moment she left the flat, I would get back into bed," he says.
He joined not one, but a few gangs. "I guess I was too sociable. I could talk to and get along with everybody. I learnt different bad things from different groups," he says ruefully.
By the time he hit his early teens, he had sniffed glue, smoked pot, popped pills and taken part in clashes with other teen delinquents.
After failing his Primary School Leaving Examination at Lianhua Primary, he was transferred to the Normal Technical stream at Bukit View Secondary School.
"When you're a Normal Tech student, you get condemned. People stereotype you," he says with a sigh.
He lived up to the stereotype of being a troublemaker although he was, he says, really not that rotten. "I had golden hair and looked rebellious but I stayed away from fighting with weapons. I really didn't like blood."
When he was about 14, he got into trouble with the law. He was out with a few friends heading towards Bukit Gombak from Bukit Batok. Some members from a rival gang thought they were crossing into their territory and spoiling for a fight.
"They waited for us and when they saw us, rushed at us and started bashing us with batons and baseball bats," he says.
Just as the fight started, the police came. He bolted home, but was arrested a few hours later.
"I was handcuffed and sitting in the police car when my father came home with the dinner he had bought for me. He came forward, and I could see the pain in his eyes. A lot of people in the neighbourhood knew my parents and I realised how much I had let them down."
He stopped his gang activities, and completed a one-year business studies course at the Institute of Technical Education in 1999.
The big change came when he started national service and was assigned to the Police Dog Unit.
"I've loved animals ever since I was small. My mother said I would happily go hungry and give my food to strays and other animals."
He found his niche learning how to handle and train canines, and won a few awards for dog handling in the force. "I read and did a lot of research, and e-mailed experts in the United States and other countries asking for advice on how to handle dogs."
Several times a week, he would also volunteer at a veterinarian's to learn more about animals. "I started out cleaning the windows but later I became the vet's assistant. I would hold the animals during surgery while the vet would explain what needed to be done and the different types of medication."
As he lacked the minimum qualifications to sign on with the police force, he was offered a six-year probationary contract after completing national service. He took the opportunity to upgrade himself, acquiring two diplomas in counselling before enrolling for a long-distance degree in psychology at the University of Southern Queensland.
His passion took him places. He was sent to Britain where he learnt how to train dogs to sniff out explosives. He also received training in police negotiation and was appointed a career counsellor for the police force.
"I was exposed to a lot. My performance was good so I was later put in a management role. I was made assistant para vet and later became the para vet responsible for the medical needs and well-being of 250 police dogs," says Mr Tan, who spent nine years with the police force. When he was 29, he decided he needed to explore other options.
"I wanted to find out what I could do," says Mr Tan, who continued working as a volunteer with various animal welfare groups.
There were stints as a marketing executive in the marine industry and as an interior designer but he did not like the jobs.
He decided to take seven months off to set up Voices For Animals, a shelter for abused and abandoned breeding dogs, last year.
"I used to volunteer at a dog shelter next to a breeding farm. I'd seen the conditions. The animals were always housed in small cages, and were often neglected. I just felt very sad for them."
A good Samaritan - whom he befriended while doing animal rescue work - offered him 1,000 sq ft of free space at Mutts & Mittens, an animal boarding house in Pasir Ris.
Setting up Voices For Animals was tough but rewarding. "There was so much to do, I'd sleep over in the shelter sometimes," he says.
The outfit, which now houses 80 animals, employs one full-time staff member. It sustains itself through donations, adoption drives and sales of souvenirs at flea markets.
"We're lucky we don't have to pay rent and we have supporters who help pay for the utilities and animals' food bills."
Earlier this year, Mr Tan was approached to become head of operations at Sunny Heights, a 30,000 sq ft day-care centre with a swimming pool for animals in Turf Club Road. He is in the process of setting up Cat Safari, a cat cafe on the premises.
With a laugh, he acknowledges that people sometimes give him a wide berth when they see his studs and tattoos.
"Every tattoo tells a story," he says, before pointing to the Chinese character ren - which means patience, restraint or control - inked on his right wrist. "I got this because I used to have an anger management issue. Now I look at this to remind myself not to fly off the handle."
He adds: "I'm not bothered by people who judge me. They don't matter."
In fact, he counts himself blessed. "Many people have stepped forward to help me when I needed help," he says.
Just then, his eyes light up as he notices a woman waving cheerily at him as she passes the cafe we are in. He waves back and says: "She's a teacher. She adopted one of our dogs and now she's also a volunteer."
Smiling, he says he has long made peace with his past.
"If I hadn't gone through what I had, I wouldn't be what I am. And I think I am sensible and empathetic," he adds, with no hint of cockiness.