Cops said Quelal Bonergy, 47, of The Bronx, hurled bolts and other debris onto the tracks at the West Fourth Street platform of the D and F lines at about 5:30 p.m., causing an ear-splitting explosion, followed by a flash of light and clouds of smoke.
Charges were pending against Bonergy, who lives in the South Bronx.
He was being interviewed by members of the Joint Terrorist Task Force because he left a suspicious package on the Fort Hamilton Army base last August. That package was harmless.
Aloa Braverman of Staten Island, who was on one of five evacuated trains, said, "I thought I heard gunshots. I thought someone was shooting. Then I saw smoke."
Sylvie Schlein, 27, of Brooklyn, who was on the same F train, said, "I heard a huge crashing sound, like a boom and a screech of the brakes.
"Soot was flying. Everyone panicked."
Passengers were taken out the back door of the last car and led single file along a catwalk to an emergency exit, she said.
An elderly man who suffered smoke inhalation and was recovering at St. Vincent's Hospital said, "We didn't know if it was a bomb, a fire or what. It was smoky and everyone was trying to get out." No one else was hospitalized.
The F, D, A and E lines in Manhattan were disrupted for several hours.
Additional reporting by Hasani Gittens
