Christopher Rossi's body was found about 11:45 p.m. Monday behind the apartment complex where he lived with his family.
Los Angeles County sheriff's deputies say he was associated with a local gang and the attack may have been related to feuding between black and Hispanic gangs in the suburban city 20 miles northeast of Los Angeles.
It was the third shooting in two days in the city nestled against the San Gabriel foothills, but Duarte Assistant City Manager Karen Herrera told City News Service that it didn't appear connected to the other two.
On Sunday, an 18-year-old black man, Malcolm Mency, was shot to death while walking home from work.
Hours later, a Latino man standing in his front yard was wounded by a drive-by shooter.
Authorities say the first shooter may have mistaken Mency, the father of a month-old boy, for a gang rival.
Rossi's body was found just a few hours after Duarte's Community Mediation Team met to discuss plans for stepping up law enforcement.
Information from: KNBC-TV, http://www.nbc4.tv/