Here is kevin tibbles. reporter: their beat is the street chicago cops erin gubala and mike nowacki. nowacki, a s.w.a.t. team medic, was pounding the pavement in full gear in a 15-k charity run. it looks kind of heavy. how about 50 pounds reporter: he also had an engagement ring burning a hole in his pocket, because girlfriend officer gubala was on duty at the finish line. but something wasn t right. on the radio, i hear him call out 4650 adam, i m administering cpr. reporter: the young woman had collapsed. her heart had stopped. so duty calls? yes yes as soon as i heard medic, i just went into medic mode. reporter: nowacki and a firefighter went to work, performing rive until an ambulance then after saving the life of one woman, nowacki finished the race, got down on one knee and asked another to spend the rest of her life with him. he pulls out this ring, and he says, erin i don t know what else to say, will you marry me of course i said yes reporter: a race