s melanie woodrow has the story. >> reporter: at the republican national convention, vice president mike pence paid tribute to david patrick underwood. >> people like dave patrick underwood, an officer in the department of homeland security federal protective service who was shot and killed during the riots in oakland, california. >> reporter: underwood wasn't in the streets of oakland the night air force sergeant stephen grio is accused of shooting and killing him. he was a contract security officer, guarding the federal building. it's context that may have been lost on anyone visiting to vice president pence last night who wasn't familiar with the story. investigators san jose grio took advantage at a time when the nation was mourning george floyd. he and his partner used the protests as a cover according to special agent in charge john bennett. >> there is no evidence that these men had any intention to join the demonstration in oak lapd. they came to oakland to kill cops. >> pat underwood was murdered because he wore a uniform. he wore that uniform to signify his authority to protect the federal courthouse. >> reporter: he's also facing charges in connection with the earlier murder of sergeant damon gus wyler. melanie woodrow, abc 7 news. >>>