WAVERLY, Tenn. -- A young father is dead, and months later his family still has not been given some very basic answers: What killed him? Why hadn't they heard from the medical examiner? Why was a basic test never done on his body?

Video: Family Searches For Answers After Father's Death

Sometime in the early morning hours of Oct. 18, Brandon McMahon died. Nearly six months later, no one knows why it happened.

"Brandon was an ideal son," said father Bob McMahon.

"It's extremely hard to not know what happened to your child," said Beverly McMahon, Brandon's mother.

What the Channel 4 I-Team learned about the death investigation into Brandon McMahon is raising questions about the state medical examiner's office.

When asked if his office messed up, state medical examiner Dr. Bruce Levy said, "I would have to say we're partially responsible."

The mystery surrounding Brandon McMahon's death started with a camping trip to the Loretta Lynn Ranch in Humphreys County. He and his twin sons went to sleep in their camper that night, but the father never woke up.

There was no sign of foul play. The 32-year-old active dirt bike rider and carpenter had no known health problems.

Still, the state medical examiner's office, which ultimately received the body from Humphreys County that day, said the autopsy and tests would reveal the answer.

"The coroner's office said 14 to 16 weeks is what we should expect," said Beverly McMahon.

But 16 weeks turned to 17, then 18, with no calls to the family on a reason for the death. Nineteen weeks, 20 weeks, 21 weeks passed with no answers.

While the wait was agonizing, Brandon McMahon's wife then learned that she could not collect on the life insurance, because the insurance company needed a cause of death certificate.

All that time, the family assumed the medical examiner's office was testing for carbon monoxide poisoning.

The local coroner's report, obtained by the Channel 4 I-Team and dated the day Brandon McMahon died, suggests that his body be tested for that carbon monoxide poisoning.

Because McMahon was found in a camper, the coroner and police suspect the odorless gas may have been to blame, even though his twin boys, who were also sleeping in the camper, were found alive.

But the Channel 4 I-Team has learned the carbon monoxide test was not performed until 19 weeks later, after the family started asking questions.

"I'm angry. Yeah, I'm angry," said Beverly McMahon.

"We're as frustrated as the family is," said Levy.

One of Levy's staff handled the death investigation. Levy said it's unclear how his office didn't know to test for carbon monoxide.

"If there was a mistake or error in communication, I would have to say it's an error on all our parts," said Levy.

Levy said even though communication has improved with outlying counties over the years, Brandon McMahon's death raises important questions:

"(Is there) a better way to do the death investigation structure than we already have?" asked Levy. "But the bottom line we're still dealing with is we have basically a healthy, young man who is dead for reasons, 20 weeks later, we can't explain."

McMahon's wife still hasn't received her life insurance settlement because there still is not a cause of death.

Levy hopes to have those tests back on the carbon monoxide poisoning soon.

The state medical examiner said the average length of time it takes for a death investigation is eight weeks. This week marks 21 weeks since Brandon McMahon died.