When's a murder become a suicide?

An Interesting Forensic Science Case At the 1994 annual awards dinner
given for Forensic Science.
AAFS President Dr. Don Harper Mills astounded his audience with the legal complications of a bizarre death.

Here is the story:
On March 23, 1994 the medical examiner viewed the body of Ronald Opus
and concluded that he died from a shotgun wound to the head. Mr. Opus
had jumped from the top of a ten-story building intending to commit
suicide.

He left a note to the effect indicating his despondency As he fell
past the ninth floor his life was interrupted by a shotgun blast
passing through a window, which killed him instantly.
Neither the shooter nor the deceased was aware that a safety net had
been installed just below the eighth floor level to protect some
building workers and that Ronald Opus would not have been able to
complete his suicide the way he had planned.
"Ordinarily," Dr Mills continued, "Someone who sets out to commit
suicide and ultimately succeeds, even though the mechanism might not
be what he intended, is still defined as committing suicide."
That Mr. Opus was shot on the way to certain death, but probably
would not have been successful because of the safety net, caused the medical examiner to feel that he had a homicide on his hands.

The room on the ninth floor, where the shotgun blast emanated, was
occupied by an elderly man and his wife. They were arguing vigorously
and he was threatening her with a shotgun. The man was so upset that
when he pulled the trigger he completely missed his wife and the
pellets went through the window striking Mr. Opus.
When one intends to kill subject "A" but kills subject "B" in the
attempt, one is guilty of the murder of subject "B."
When confronted with the murder charge the old man and his wife were
both adamant and both said that they thought the shotgun was not
loaded.

The old man said it was a long-standing habit to threaten his wife
with the unloaded shotgun. He had no intention to murder her.
Therefore the killing of Mr. Opus appeared to be an accident; that
is, assuming the gun had been accidentally loaded.
The continuing investigation turned up a witness who saw the old
couple's son loading the shotgun about six weeks prior to the fatal
accident. It transpired that the old lady had cut off her son's financial
support and the son, knowing the propensity of his father to use the
shotgun threateningly, loaded the gun with the expectation that his
father would shoot his mother. Since the loader of the gun was aware
of this, he was guilty of the murder even though he didn't actually
pull the trigger.

The case now becomes one of murder on the part of the son for the death of Ronald Opus.

Now comes the exquisite twist.
Further investigation revealed that the son was, in fact, Ronald Opus.
He had become increasingly despondent over the failure of his attempt
to engineer his mother's murder.This led him to jump off the
ten-story building on March 23rd, only to be killed by a shotgun blast passing through the ninth story window. The son had actually murdered himself.
So the medical examiner closed the case as a suicide.

A true story from Associated Press, (Reported by Kurt Westervelt)