The day Lyvette Crespo allegedly shot and killed her husband, Bell Gardens, Southern California, Mayor Daniel Crespo, at their condo, it ended 28 years of physical abuse against her and her son, a source close to the mayor's wife told NBC4.

During a domestic dispute in front of their son Tuesday, she grabbed Daniel Crespo's gun – the one he used as a probation officer – and opened fire, killing her husband, the source said.

Lyvette Crespo was detained Tuesday, but was released after questioning.

Police and prosecutors were not talking about the case on Wednesday.

The source close to Lyvette Crespo said the mayor abused his wife for years.

The abuse started as far back as the couple was together, but Lyvette kept the abuse secret, the source said.

She didn't seek medical attention for those cases nor report them to police.

It's unclear when the physical abuse started with the son, but had been ongoing for at least the last four years, the source said.

Bell Gardens police officials have no reports of domestic violence calls to the Crespo's Bell Gardens condo.

Crespo has been described by family and friends as a nice, generous and giving man. Some neighbors said there was no indication of violence at the home.

"He worked at the County Probation Department where he was helping young adults to better themselves. So he was always trying to find alternative ways to…you know, violence was not an option," friend Albert Bernal said.

He sat on the Bell Gardens City Council for 13 years before becoming mayor. A biography on the city’s website said Crespo married his high school sweetheart.

The city's Mayor Pro Tem Priscilla Flores said she is in shock.

She described him as a good person, his wife as quiet and nice and his children as ideal.

"As a colleague and a friend, I knew his heart was always in the right place," Flores said in a statement.

Friends of Crespo plan to hold a vigil at City Hall Friday evening.

NBC4's Tena Ezzeddine contributed to this report.