Convicted Boston Marathon bomber Dzhokhar Tsarnaev has been moved to the United States’ most secure prison where he will be confined to a small concrete room for 23 hours per day with little contact with the outside world, the Boston Globe reported.

Tsarnaev was instead moved to ADX Florence, the Associated Press reports.

A federal jury sentenced Tsarnaev to death in May for his involvement in the 2013 bombings at the marathon.

Typically, inmates who are awaiting a federal death sentence are held in Terre Haute, Ind., which the Bureau of Prisons has designated as its facility for carrying out executions. The prison, known as the “Supermax”, is in the same complex as the penitentiary and houses some of the country’s most notorious criminals, including 9/11 conspirator Zacarias Moussaoui and Unabomber Ted Kaczynski.

Tsarnaev was convicted of 30 charges in the marathon bombings, which killed three people and injured more than 260. Tsarnaev also was convicted of killing MIT Officer Sean Collier during the getaway. ‘I regret ever wanting him to speak…

Following the bloody bomb attacks, his older brother Tamerlan, 26, was shot dead by police, leaving Dzhokhar to stand trial alone after he was captured.