Kevin Spacey‘s rescue dog — named Boston in honor of the city after the Boston Marathon bombings in 2013 — has died … TMZ has learned.

Sources with direct knowledge tell us … Boston, a mixed breed, passed away at a doggie daycare in Baltimore on Tuesday. We’re told Kevin left her there at least 8 months ago when he headed to London for work, but kept up daily FaceTime calls with his pup across the pond.

Boston had been Spacey’s constant travel companion for years, but she recently got sick. We’re told he wrestled with the idea of flying back to the States, but Boston’s doctor urged him to act quickly to prevent more suffering, and Kevin didn’t want her to wait until he arrived.

Kevin first introduced Boston to the world in May 2013, tweeting her original name was Cuddles, before he adopted her after forming a special bond during a trip to the city to support recovery efforts after the marathon bombing.

Boston was around 13 years old.