Authorities say they have no motive for the deadly shooting that killed Alva, who friends say was studying engineering at Long Beach City College.
"It really is out of character for the neighborhood," said Sheriff's Detective Dave Coleman.
Coleman says Alva was likely targeted, but investigators are trying to figure out why.
"We believe the individuals were there because they knew the victim. It just wasn't a random walk-up or walk-by, we don't believe," Coleman said.
Investigators are searching for two suspects who were seen running from the scene of the shooting on the 3700 block of Arbor Road at around 1:55 p.m. Thursday. The suspects were seen getting into an older model white four-door sedan, possibly a Toyota Camry.
According to investigators, the suspects walked up to Alva as he stood in the front yard of his home, and at least one of those suspects opened fire at close range. Alva was struck in the torso and died outside at the scene.
Loved ones gathered Thursday night for a vigil in his honor. His mother, who attended the vigil, described her son as a good boy who loved everyone and never hurt anyone.
If you have any information that can help investigators track down the suspects, call the Los Angeles County Sheriff's Homicide Bureau at (323) 890-5500 or contact Los Angeles Regional Crime Stoppers at (800) 222-TIPS.