Authorities responded to the 8100 block of Webb Avenue at about 11 a.m. The 21-year-old pedestrian and his pit bull puppy were declared dead at the scene.
The Metro bus was heading south on Webb Avenue when authorities say a man ran out into the street chasing a dog that had darted off after a ball.
"From what I'm told, he had just picked up the dog when he was struck by the bus," said LAPD Capt. Maureen Ryan.
Morcell Shelby, the victim's brother, unknowingly came upon the accident that killed his brother, who he identified as Xavier Shelby.
"I don't know what to think. I don't know what happened," he said.
Shelby said his brother walked the puppy daily. Witnesses say the man was talking with friends on the sidewalk, playing catch with the dog, when the ball bounced into the street.
"It's just an absolute tragedy that we have a loss of life here in the Valley," Ryan said.
The accident remains under investigation.