Police say a convicted sex offender who escaped near Dallas while being transferred from Florida to Nevada allegedly told former cell mates he would never return to prison.

Grapevine police said Wednesday that the former cell mates of 42-year-old prisoner Alberto Morales told investigators he had made the promise.

Morales has been a fugitive since police say he stabbed one of the two Miami-Dade detectives who were transferring him Monday while they were in Grapevine awaiting the arrival of a third officer who was flying in to join them.

Police say Morales became disruptive on the flight to Houston so his escorts decided to rent a vehicle to drive the rest of the way.