The gang signs and flashing cash are a hint about what mattered to him, who his associates were and thus who probably killed him.
He looks a little older than 14.
The sign on the left looks like a “b” for Bloods and fits his red clothing. The sign on the right looks like something I just saw Marshawn Lynch flashing in a photo of him doing community outreach overseas. I think some of these pro guys try to get smart (like Lynch might be flashing a ML), or perhaps it is a neighborhood sign (Lynch is from Oakland) - but it all looks so stupid.
My son was going through that phase awhile ago flashing stupid signs for photos. He went on a church mission trip to California years ago - and I told him to knock it off - that might be enough to get killed for in some neighborhoods.