A person was pulled from the water at Walden Pond Friday afternoon, authorities said.
According to Massachusetts State Police, officials responded to Walden Pond around 4:30 p.m. Friday after receiving reports of a man struggling in the water.
Bystanders say they were able to pull the man from the water and begin CPR before first responders arrived on scene.
Police say responders also performed CPR on the man before he was taken to the hospital.
The man is expected to survive.
The man's exact age is not known, but Concord police say he is an older adult.