Honolulu firefighters rescued a man in his 40s who suffered cardiac arrest while hiking up Koko Crater stairs trail on Wednesday evening.

The Honolulu Fire Department received a 911 call at about 5 p.m. for a hiker experiencing a medical emergency at Koko Crater in Hawaii Kai. Six units with 17 personnel responded.

The first unit to arrive climbed up the trail by foot.

Bystanders started CPR after the patient went into cardiac arrest on the stairs, continuing until firefighters reached the hiker at 5:19 p.m., according to HFD. Firefighters conducted a medical assessment and took over CPR.

HFD’s Air 1 helicopter airlifted the man to a landing zone, where care was transferred to Honolulu Emergency Medical Services at 5:38 p.m.

Paramedics treated him and took him to a hospital in critical condition.