Police Officer Gunther Hashida was found dead at his home on Thursday, the report said.
Police Officer Jeffrey Smith and US Capitol Police Officer Howard Liebengood had also responded to the Capitol riot and later died by suicide.
On January 6, a group of supporters of former President Donald Trump entered the US Capitol in a bid to protest the lawmakers certifying the 2020 election results from several states Trump said were fraudulent. One protester was shot dead during the incident and federal law enforcement authorities have charged more than 500 people for their participation in the unrest.