(CNN) A service dog is believed to be the first to reach the summit of Mount Rainier.

The medical alert dog, Loki, made the trek with its owner, Elizabeth Briggs. They were joined by Mel Olson and McKenzie Johnson, who led the journey. This was Johnson's seventh Rainier summit.

This particular climb has been two years in the making, starting when Johnson and Briggs met.

"The topic of climbing Rainier came up almost immediately after we met and the idea intrigued me," Johnson said. "Though I knew it would take more planning and education than the usual trip up Rainier, it was something I wanted to help them do."

In the last two years, Johnson, Briggs and Loki have spent time hiking, ice climbing, and completing a winter Colorado "14-er" (a mountain peak exceeding 14,000 feet) to prepare to take on Rainier.

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