Crespo, 45, was shot about 2:30 p.m. at his home in the Vinas la Campana condominium complex in the 6300 block of Gage Avenue during an argument with his wife, 43, and his 19-year-old son, said Nicole Nishida, Sheriff's Department spokeswoman.
An altercation between Crespo and his wife began in the master bedroom. At one point, his son, Daniel, intervened, Nishida said. While father and son were fighting, Crespo's wife got a gun and shot him, Nishida said.
Crespo died en route to a hospital, Bell Gardens Fire Department officials confirmed.
Levette Crespo was questioned but was released without an arrest being made, according to the sheriff's officials.
All evidence will be presented to the district attorney's office to determine whether charges will be filed, according to the officials.
Crespo's son was taken to a hospital for injuries to his face from the struggle and was then questioned by authorities, according to sheriff's officials.
Residents say that Crespo and his family have lived at Vinas la Campana for years.
The complex consists of beige two-story condos that are close to Gage and Garfield avenues, near City Hall.
"It's a horrible day," said Ana Maria, a condo resident. "He was such a nice man and was so important to the city."
Eric Noriega, 39, said he was napping in the living room when he heard three loud pops between 2 and 2:30 p.m.
"We didn't really know what to make of it," Noriega said. "We were about to leave the building later when we saw that police had cordoned off the area."
The incident comes a year after Crespo and several other council members were the subject of threats posted on Facebook. According to an article published at the time by EGP News, the City Council decided to cancel a public meeting because of the threats.
Born in Brooklyn, Crespo was a teenager when he married his high school sweetheart in 1986, according to the Bell Gardens website. The couple moved to Bell Gardens, and they had a daughter in 1987 and a son in 1994, the website says.
Crespo was first elected to the City Council in 2001 and worked as a Los Angeles County probation officer for more than a decade, a job he continued to hold after becoming mayor last year, according to the city.