George Gilmore, 32, of Rockland was arrested in the bathroom of a local business Wednesday after leaving the scene of the stabbing.
Police were called to an apartment on Knox Street around 12 p.m. earlier in the day.
They found a 33-year-old man and his 28-year-old girlfriend had been stabbed by another person living in the apartment. Both victims were taken to Penobscot Bay Medical Center.
The man was then taken by LifeFlight to Maine Medical Center because of the extent of his injuries.
The woman was later released from Penobscot Bay.
Gilmore was also treated and released into police custody. He's charged with elevated aggravated assault and aggravated assault with a deadly weapon.
He's being held at the Knox County Jail.