We Never Know
No Slack
It doesn't say "their client" was in the car.To be fair, SS is not law enforcement; they are bodyguards. Their job is to protect their clients, often times by any means necessary, and the high status of their clients truly guarantees "by any means necessary"
It says 'they caught three people attempting to break into a parked, unmarked Secret Service vehicle in the area'
Edit:: The news just reported it was parked outside her home so evidently she wasn't in it.