Auburn Grad Was Shot During Boyfriend's Father's Antique Gun Demo, Cops Say

An autopsy report is filling in the blanks in Auburn grad Whitney Robeson's death ... alleging a casual show-and-tell of antique firearms ended with a deadly gunshot.

According to the Jefferson County Coroner, Whitney was visiting Alabama with her boyfriend on March 7 when his dad allegedly pulled out a collection of antique firearms to show the couple. Investigators say he was handling a Colt Navy single action revolver when the gun -- which he allegedly didn't realize was loaded -- fired a single round into Whitney's chest.

As we reported ... Jeffrey Scott Towers -- the father of Robeson's partner -- was arrested and charged with manslaughter last week, 2 months after Whitney's death. He was released from jail after posting a $30K bond.

Examiners determined the bullet tore through Whitney's left lung, heart, and aorta ... causing catastrophic internal injuries. Whitney was rushed to a Birmingham hospital, where doctors tried to save her life ... but she was pronounced dead shortly after arriving.

The medical examiner ruled her death a homicide.

Her family also is pushing back hard against claims the shooting was just a tragic accident ... with their attorney telling TMZ the suspect’s actions amounted to "criminal recklessness" after prosecutors charged him with manslaughter in the fatal March shooting.

In a statement though the attorney, the family said they are "deeply saddened by the circumstances surrounding this case" and added ... "At its core, this matter involves the tragic and unnecessary death of a 22-year-old young woman whose life was cut short far too soon. Whitney was a daughter, loved one, and member of her community, and that should never be lost in the discussion surrounding this case."