A Maui man already locked up for an armed carjacking will now spend twice as long behind bars, a result prosecutors are calling a win for public safety.

• Christopher Steven Helmer got another 10 years in prison, bringing his total to 20.
• The new sentence covers holding his girlfriend at gunpoint overnight in Honokohau Valley.
• That happened weeks before he took a California couple's car at gunpoint and fired a shot on Pi'ilani Highway.
• The couple hid from him on Haleakala for almost a full day before he was caught.
• His father said two years ago that his son was addicted to drugs and needed help.

Outlook: With both sentences stacked, Helmer stays in prison for the long haul unless an appeal changes that.