Mr Gerrand worked hard for his scholarship dream and had only been in the US for two weeks when it turned into a nightmare.
"I was walking past going to my classes and then just heard gunshots and saw people falling pretty much," he told Radio New Zealand.
His former coach Jeff Green said Mr Gerrand was understandably shaken.
"He was running alongside a guy and the guy was shot dead - the guy running next to him.
"He ran past three others that were shot dead, so it was horrifying, horrific. So he saw four people dead. He's totally distressed."
Mr Gerrand's family said yesterday they were making plans to fly to his side.
In a statement, mother Moretta Gerrand said the family was devastated by the incident.
"Jaylen has not been injured, but was involved," she said.
"We are hoping to travel to be with him. Jaylen has made many friends in his short time in Oregon and wants to be able to be there for them."
His mother was last night making arrangements to travel to Oregon as soon as possible.
In New Zealand her son was a member of the New Zealand Breakers basketball academy.
In April this year he set up a Givealittle page describing his efforts to get to the US.
On it, Mr Gerrand said he'd dreamed of playing basketball in the US since watching his first NCAA basketball tournament with his father. "I love anything and everything basketball," he wrote.
"I grew up watching my parents play competitively ever since I can remember. This sparked my passion for the sport which I started playing at 8 years old at Orewa Primary, all the way through to my last days at Westlake Boys High School."
However, he said his family and financial situation had challenged him after his parents separated three-and-a-half years ago.
At just 15, he worked hard to support his mother and then 1-year-old twin brothers while still attending school and playing basketball, both locally and nationally.
"That first year was incredibly hard for our family and since then many sacrifices have been made and I have had to decline opportunities due to our financial situation."
Two other Kiwis, Tamamoko Green and Hyrum Harris, were set to join Mr Gerrand in the US on Tuesday after the New Zealand secondary school national basketball championships.
But the Umpqua basketball coach had postponed their travel and the college was expected to be closed for at least a week as police investigations continued.
The tragedy was the 293rd mass shooting in the US this year, reigniting the country's gun-control debate and sparking strong comments from President Barack Obama, who had previously raised the need for gun controls that Congress and Senate seemed unwilling to move on.
"The tragedy for the United States in recent times is that this isn't the first and sadly it doesn't look like it's going to be the last," he said yesterday.
"The United States has hundreds and hundreds of millions of guns in circulation. From Virginia Tech to the most recent in Oregon we've just seen far too many innocent people killed as a result of that."
NZ police probe copycat threat
New Zealand Police last night started an investigation into a copycat shooting threat here linked to the Oregon massacre.
US authorities are examining a post in an online forum linked to Chris Harper Mercer's rampage that killed 10 people - including himself - and left seven injured yesterday.
New Zealand Police last night confirmed they were investigating a post on the same forum, which the Weekend Herald has chosen not to identify.
The post warned of a New Zealand "beta uprising", which was the same reference made in the US post.
"Beta" is a slang term for school students who are not considered among their peers to be socially elite or "alpha" students.
It was too early to say how credible the threat was, but a police spokeswoman said such comments were taken seriously.
"Police are now aware and are currently looking into this," she said.
