The news comes shortly family of officer Gunther Hashida confirmed that he died by suicide on 29 July.
Metropolitan Police Chief Robert J Contee III notified the force of the death of Mr DeFreytag, who served in the 5th District at the Capitol to enforce curfew violations, WUSA9 reported.
“I am writing to share tragic news that Officer Kyle DeFreytag of the 5th District was found deceased last evening,” Mr Contee wrote in mid-July. “This is incredibly hard news for us all, and for those that knew him best.”
US Capitol Police officer Howard Liebengood was the first to take his own life three days after the Capitol riot, followed on 15 January by officer Jeffrey Smith.
Watch: Select committee investigates Capitol riots
While Mr DeFreytag was the third to die by suicide, news of his passing came just hours after confirmation of Mr Hashida’s death. He leaves behind a wife and three children after reportedly being found dead in his home.
“We are grieving as a Department as our thoughts and prayers are with Officer Hashida’s family and friends,” a spokesman for the department told DailyMail.com on Monday.
News of the two suicides comes a week after Capitol and DC Metropolitan Police officers testified before the House select committee investigating the Capitol riot.
During the hearing, officers recounted being beaten, crushed, shocked, sprayed with chemicals and subjected to death threats and racial slurs by the Trump supporters who attacked them during the riot.
The families of the officers who took their own lives said they noted a change in their loved ones in the wake of the riot.
“I do believe if he did not go to work that day, he would be here and we would not be having this conversation,” Mr Smith’s wife Erin told The New York Times.
DC Metropolitan Police Office Michael Fanone told the House select committee that he has suffered from post traumatic stress after his experiences during the Capitol riot.
Watch: Barricades come down on US Capitol as threat level lowered