Updated

Czech news agency CTK has reported that an American who was convicted of killing four of his Czech relatives has killed himself in prison.

The agency says Kevin Dahlgren killed himself Thursday in the Valdice prison northeast of Prague where he was serving a life sentence.

Prison service spokeswoman Petra Kucerova confirmed a prisoner died but gave no details, citing an ongoing investigation.

In 2016, a Czech court convicted Dahlgren of killing the father, mother and their two sons in their home during his visit to the Czech city of Brno on May 22, 2013.

An appeals court upheld the life sentence last year.

Dahlgren, of Palo Alto, California, was detained at Washington Dulles International Airport following the killings and was extradited to the Czech Republic in 2015.