COCONUT CREEK, Fla. – Just a few months before the mass shooting at Marjory Stoneman Douglas High School, 19-year-old gunman Nikolas Cruz tried to buy an AR-15 rifle at a Coconut Creek pawn and gun shop, but he was turned away because of his age, the owner told Local 10 News in an exclusive interview.

"He was cool. He was quiet. He was not nervous at all," the owner of Coconut Creek Pawn & Guns said.

Razi is still shaken, so much so that he's asking Local 10 not to use his last name.

Deputies said Cruz killed 17 people and wounded more than a dozen others when he opened fire with an AR-15 rifle inside the Parkland school on Feb. 14.

The Broward Sheriff's Office interviewed Razi on Tuesday as part of its investigation into the school shooting.

"And I asked him, it's the first question I ask everybody, 'How old are you?'" Razi recalled. "And I believe he said, 'Oh, I'm over 18.' I said, 'Are you under 21?' He said, 'Yes,' and I said, 'I don't sell any firearms to under the age of 21.'"

The store owner said Cruz tried to persuade the owner to sell him the rifle.

"And I said, 'Because I don't need an 18-year-old to buy (a) weapon and clear out his high school with it," Razi said.

Razi said that's the message he gives to everyone Cruz's age.

"Not just him," Razi said. "I tell it to every kid who comes here to buy weapons."

It's legal in Florida to sell rifles to people 18 years old and older. Gov. Rick Scott is expected sign a bill spurred by the Parkland shooting that raises the age to 21.

Razi said he didn't make much of the encounter at the time. He first heard about the tragedy while he was traveling in Israel.

He recently returned to Florida and found a review about him from a Nikolas Cruz.

"Very judgmental and denied me customer service," the review said.

"And I logged in online and looked for a picture of him, and when I saw the picture of him, I said, 'Yep, I knew he was in my store,'" Razi said.

Razi said his policy on selling guns may bring him less business, but he stands by his decision.

"I have chills really coming down my spine," Razi said. "I mean, thank God I have not sold this monster a weapon."