ELLIS COUNTY - National Transportation Safety Board investigators are on the scene of the CareFlite helicopter crash near Midlothian.
They want to know why it crashed yesterday, killing the two people on board.
CareFlite lost two of their own, a pilot and a mechanic.
They have been identified as Stephen Durler, 23, of Dallas (the mechanic) and Guy Joseph Del Giudice, 44, of Keller (the pilot).
"I've been in aviation for 35 years. I flew in the military, I flew in the airlines, I've flown in EMS and yesterday was the worst day that I have ever had in all that time," said Jim Swartz, president and CEO of CareFlite.
"As you know, first responders are a tightly-knit group and there's a lot of pain and they need the empathy and appreciation from the public," said NTSB investigator, Tom Latson.
The helicopter was on a post-maintenance test flight when it went down, just after 2 p.m. on Wednesday, soon after it had left its hanger in Grand Prairie.
What stands out to investigators is that its main rotor appears to have somehow separated from the fuselage.
There was no flight recorder or voice recorder on board the helicopter. They are not required.
The trail of debris from the crash runs 1500 feet long and investigators found the three main parts of the helicopter in three separate places.
The entire rotor system, which had both blades intact, was found in one spot; they found the tailboom in another spot and the main fuselage, which exploded, in yet another spot.
Investigators will seek to interview witnesses and study the craft's structural and electrical components, Latson said on Thursday.
"We're all one big family, so to see one go down is like watching your brother or sister go down," said EMS worker Kyle Barnett. "It breaks your heart."
There were no patients on board the CareFlite at the time of the crash.
According to CareFlite, it purchased the helicopter just three months ago from Addison-based Omniflight. In a statement issued Wednesday night, Omniflight said the Bell 222 was in airworthy condition at the time of the sale.
Records show aircraft operated by Omniflight were involved in five accidents over a six-month period, ending in February, including a crash at Fort Bliss in El Paso, which killed three people.
Associated Press contributed to this report.