It happened on the 200 block of Main Street.
The victim was taken to the hospital where he later died.
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It's unclear if anyone has been arrested.
Police said the motive and circumstances involving this shooting are under investigation at this time.
The victim's identity is being withheld pending next of kin notification by the Solano County Coroner's Office, police said.
This is Vallejo's 6th homicide this year.
Anyone with information on this case is asked to contact Detective Brian Murphy at (707) 648-5430 or Detective Ken Jackson at (707) 648-4280.
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