A Woodbury police dog in service since 2007 has died unexpectedly while off duty at home.

Niko, one of three K-9 dogs at the Woodbury police department and a member of the Washington County SWAT team, was trained for tracking suspects and missing persons, searching buildings, finding evidence and apprehending lawbreakers. He also was trained to detect drugs.

“He was a one-person dog and I was his one person, so it’s tough,” his handler, officer Jason Posel, said Friday.

Niko’s death, which occurred Monday, wasn’t related to his K-9 work. Preliminary results from the University of Minnesota show that internal bleeding, possibly from two stomach ulcers, caused Niko’s death, Posel said.

“It’s hitting the entire family pretty hard,” said Posel, who had trained Niko since he was 15 weeks old.

Niko was the second K-9 dog for Posel, who has trained K-9 dogs in Woodbury for 13 years.

In 2011 and 2012, Niko received perfect scores and won first place at the U.S. Police Canine Association Narcotics Certification.

Posel described him as “a very fast dog” and said he exhibited a “strong drive to work.” His keen sense and high level of training led to numerous arrests, including catching a suspect in a violent domestic assault.

As a Belgian Malinois, the first-ever such breed at the Woodbury department, Niko was smaller than a German shepherd. He began training in Woodbury in the summer of 2007.

Niko also was a staple at many public education events, demonstrating his agility and obedience for Safety Camp participants, Woodbury Days guests and many other local and regional events.

The department will remember Niko as a fearless, highly intelligent and tenacious police dog, said police spokeswoman Michelle Okada.

The Woodbury police department has two other K-9 dogs, Bosco and Nova.