The Boston Marathon bomber Dzhokhar Tsarnaev will still face state charges in the death of a Massachusetts of Institute of Technology police officer, even though he is now on death row inside a federal prison, a prosecutor said.

Middlesex County district attorney Marian Ryan told the Boston Globe it was appropriate to continue with the case considering Tsarnaev’s federal convictions are not final, pending appeal.

Tsarnaev, 21, was sentenced to death last month after being convicted of federal charges in the April 2013 bombing that killed three people and injured more than 260. Some of those charges related to the shooting of officer Sean Collier by Tsarnaev and his older brother Tamerlan days after the bombings, as they tried to flee the area.

The Tsarnaev brothers carjacked a Boston man and briefly held him hostage. Police tracked the brothers to nearby Watertown, where Tamerlan died after a shootout with officers. Dzhokhar was captured several hours later after an intense manhunt, hiding in a boat in a backyard in the Boston suburb.

“When you come into Middlesex County and execute a police officer in the performance of his duties and assault other officers attempting to effect his capture, it is appropriate you should come back to Middlesex County to stand trial for that offense,” Ryan said.

Ryan’s office said it was beginning the process of seeking Tsarnaev’s return to the state from federal custody and it was unclear when he could be tried. A message seeking comment was left with Ryan’s spokeswoman.

Tsarnaev’s defense attorney on the state charges, John Salsberg, declined to comment.

A Middlesex grand jury indicted Tsarnaev in June 2013 on the charges that also include carjacking and kidnapping. Boston prosecutors decided not to pursue separate state charges.

Tsarnaev is at the high-security federal prison in Florence, Colorado.