His only son, Vincent, who used to help him, was in prison.
The old man wrote a letter to his son and described his predicament:

Dear Vincent,
I am feeling pretty sad, because it looks like I won’t be able to plant
my tomato garden this year. I’m just getting too old to be digging up a
garden plot. I know if you were here my troubles would be over. I know you
would be happy to dig the plot for me, like in the old days.
Love,
Papa

A few days later he received a letter from his son::

Dear Pop,
Don’t dig up that garden.
That’s where the bodies are buried.
Love,
Vinnie

At 4 a.m. the next morning, FBI agents and local police arrived and dug
up the entire area without finding any bodies. They apologized to the old
man and left.

That same day the old man received another letter from his son::

Dear Pop,
Go ahead and plant the tomatoes now.
That’s the best I could do under the circumstances.
I love you,
Vinnie