Police arrested Chouinard at his home Saturday night and charged him with one felony count of aggravated assault. Conviction could result in five to 15 years in prison.
Police said Chouinard grabbed his wife, Erica, by the throat and slapped her, causing minor injuries to her face and neck. He also put the gun against his head and threatened to kill himself, according to police records.
The pitcher was freed after posting bail of $32,000 bond. He could not be reached for comment.
"He came within a bazillionth of an inch of killing his wife, and we take that quite seriously," said Bill FitzGerald, a spokesman for the Maricopa County attorney's office.
FitzGerald said his office wants to send a strong message against domestic violence, after a year during which there were a record number of domestic homicides.
He said prosecutors do not expect to reduce the charge even though this is the first time Chouinard faces a criminal charge.
Erica Chouinard, 26, told the court she fears for her safety and sought a restraining order against him. She also said she will file for separation.
Chouinard was 5-2 with one save and a 2.68 ERA in 32 games last season.
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