UPDATED 08/02/11 7:50 a.m.

CHICAGO (CBS) — A 19-year-old man is dead, after being pulled unconscious from Lake Michigan Monday night offshore from the Ohio Street Beach.

Police were called to the beach after a woman flagged down officers around 9 p.m. and said someone was drowning, police News Affairs Officer Amina Greer said.

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The man swam to a buoy about 50 yards offshore and some distance south of the beach, but couldn’t make it back, Fire Media Affairs spokesman Joseph Roccasalva said.

He was part of a group of friends who had gone out for a nighttime swim.

Roccasalva said Fire Department divers, working with assistance from Police and Fire Department helicopters, located the man.

Paramedics performed cardiopulmonary resuscitation on the man as he was taken to nearby Northwestern Memorial Hospital, but he did not survive.

The man, identified as Javier Rivera, 19, of the 1300 block of Santa Anita Drive in Hanover Park, was pronounced dead at Northwestern Memorial Hospital at 10:24 p.m., according to the Cook County Medical Examiner’s office.

The Sun-Times Media Wire contributed to this report.