The shooting happened just before 5 p.m. at 87th Street and Denker Avenue, according to the Los Angeles Police Department.
Investigators said Birdsong was shot about seven times. The suspect vehicle was described as a dark SUV.
The boxer's mother Zonyia Birdsong told Eyewitness News that she watched gunmen kill her son outside her home.
"It's just senseless. It don't make sense to me," Zonyia said.
Birdsong was the reigning World Boxing Foundation International welterweight champion. He was scheduled to fight on Oct. 26.
"I don't know how to process it," Zonyia said. "He's a triplet. I lost his other two brothers at birth. He survived it... It's like I'm numb."
Zonyia said her son came home to join the family for dinner. Before he could get out of his car, gunmen drove up and started firing at him.
Zonyia said her son exited his vehicle and took off running, and he was followed while being shot at. She said as her son fell to the ground on the side of her home, he was shot and killed.
"They murdered my child in front of me," Zonyia said. "Who does that?"
Police said two gunmen shot and killed Birdsong and took off in a getaway car. Police are searching for the shooters and a motive.
Birdsong's family said he was not a gang member or a troublemaker. They said his passion was boxing and helping the less fortunate.
"He would pass out food and ask homeless people, the less fortunate what size do you wear? Are you hungry?" Zonyia recalled. "And then he would sit with them and talk with them and ask them what happened."
No arrests have been made.