Dr King's LinkedIn profile stated he ran the Māori Disease Reversal Project, a 45-day dietary intervention programme and academic study, in Hastings and Flaxmere last year.
During this time, between March and June, Dr King stayed with Lisa and Paul Watson in Pakowhai.
Mrs Watson said her family was shocked to hear about his death last night.
"We were horrified at the thought of what happened to him, he's the least aggressive person we know.
"We were quite devastated to know that such a good-hearted person had such a tragic end.
"He was such a warm and very, very nice man and he was very passionate about what he did."
The Watsons saw him daily during his stay and he would share his research and ideas with them.
"He really wanted to help people...and he was always talking to us about what he was doing, passing on the knowledge that he had.
"He was especially wonderful with our three children and would have a kick-around with them in the back yard and come to their soccer games. He became like one of the family."
Dr King was due to stay with the Watsons in a few weeks time while on a trip to New Zealand to hold a workshop on his research It's Not Sweet As: the Flaxmere disease reversal in Māori project at the FIZZ Symposium in Auckland about taxing sugary drinks on June 26.
Mrs Watson said she had just been talking with her husband a few days ago about how it was strange they had not heard from him to confirm the dates of his stay.
A Boulder police and fire departments spokesperson said police had been investigating the shooting which occurred shortly after midnight on May 29 following an argument between two people.
It started inside the restaurant before moving outside where shots were fired.
A seven-page witness affidavit, which was produced at a hearing on Thursday and has been supplied to Hawke's Bay Today, stated that when police arrived at the scene Sebastian was being subdued by restaurant staff and claimed that he was "acting in self-defense as the victim attacked him".
Witness statements confirmed Dr King and Sebastian had met at a party on May 28 and afterwards had gone with several guests to the Bramble and Hare restaurant for dinner.
One of the hosts, Leah Akin, had meant to invite a female friend called Chris King but accidently sent the invitation text to Dr King, who she had "hooked up" with several times, however, when he showed up she welcomed him to the party.
Sebastian had been invited by co-host Gary Reeves who had known him a year but was uncomfortable around him due to him talking about his interactions with the "mob".
One witness said Akin and Sebastian were flirting and kissing at the party, which given the past relationship between Akin and King, had caused an awkward situation.
Witnesses claimed Dr King and Sebastian were arguing about politics throughout the meal.
Their dispute became heated when the bill came because the group were $100 short.
Both men were seen leaving the restaurant and shortly afterwards gunshots were heard, the statement said.
Witnesses then saw Dr King re-enter the premises falling on the ground followed by Sebastian who fired two shots at close range.
Boulder County District Attorney public information officer Catherine Olguin said Sebastian is currently being held without bond in the Boulder County Jail and is due to next appear in court on August 7.
Sebastian was also charged with illegally carrying a concealed weapon.
First degree murder is a class one felony punishable by life imprisonment or the death penalty in Colorado.
Dr King worked with Māori in Hastings to reverse obesity and metabolic disease during the Māori Disease Reversal Project.
He stated in his overview of the project that "Māori suffer from some of the world's highest rates of obesity, gout, cancer, and cardio-renal-metabolic diseases in the world".
The programme and study involved intensive education and training to show participants how to make changes to their diet with results including weight loss, triglyceride levels lowering and a drop in uric acid levels.
