Concerns over ambulance response times in the wake of a teen's death have led to change in Surrey.

Two years ago, 15-year-old Dario Bartoli died after a violent assault. No one has been charged in his death.

Police arrived at the scene to find the teen seriously injured, and called for paramedics to rush the boy to hospital.

But the Surrey fire chief said RCMP were put on hold for three minutes when they called the B.C. Ambulance Service. When no ambulances arrived at the scene, police had to call back and ask again for a vehicle to come to the scene. The Provincial Health Service Authority (PHSA) said it took 21 minutes for an ambulance to arrive.

So the fire chief, Len Garis, wrote a letter expressing his concerns to Linda Lupini, the executive vice-president of PHSA. 

"I am writing you to inform you about some serious concerns with...what appears to be inconsistencies with how the pre-hospital care system operates," he wrote in January 2015.

Another part of the letter reads, "With civilian emergency requests for service, it is imperative that the emergency services (Ambulance, Fire & Police) have stable and consistent systems in place so the broader service can be reliably and consistently provided."

Lupini said the letter prompted an extensive review of ambulance response times. She said after they read it, they looked over the entire process, from a call coming in to paramedics arriving on-scene.

"In doing the review, we did see some things we could improve," Lupini told CTV News on Monday.

"We did a lot of internal review and a lot of internal discussion and we believe we've improved the process significantly since then."

They also looked at all aspects of processing a call, including how calls are prioritized. Sometimes calls need to be put on hold because of the volume, but they try to take basic information from the caller from the beginning to help determine the urgency.

"Obviously everybody taking the calls, everybody deploying ambulances and every paramedic that attends is trying to do their best in a situation like that, but it does happen," she said.

She said that the PHSA is now working more closely with Surrey Fire, and that they've added an additional three ambulances to the city's fleet.

PHSA has improved its process, and "we think we are doing a better job than we were doing then," she said.

Officials don't know whether a faster response time would have made a difference for Bartoli, Lupini said, but the case was taken very seriously.

"An organization like ours is always trying to improve," she said.

With files from CTV Vancouver's Michele Brunoro