( CNN ) -- Marie Mills held her 77-year-old father , who had collapsed outside in a Washington street . She screamed for help . A passerby rushed across the street to bang on the door of a fire station , knowing that firefighters are trained to provide emergency medical help . But they would n't leave the station . The same thing happened when two more people tried to summon the firefighters for assistance , Mills says . `` We looked across the street at the fire station . There was a firefighter that was actually standing against the fire apparatus , '' she told CNN affiliate WJLA . `` Everybody started trying to wave him over . '' But the firefighter said he had to be dispatched first . `` I even ran to the curb and said , 'Are you going to help me or let my dad die ? ' '' said Mills . Later , after an ambulance finally arrived , Cecil Mills died at a hospital . He had suffered an apparent heart attack . An investigation is under way and , so far , no officials are publicly challenging Mills ' version of events . `` It 's an outrage , '' Washington Mayor Vincent Gray said at a news conference . `` I was absolutely furious . '' He said he apologized to Marie Mills for `` what appeared to be dereliction , '' DC news station WTTG reported . `` Those who failed to respond as they should -- they will be held accountable , period , '' Gray vowed . In comments Thursday to CNN , Gray said he has `` taken a lot of time with it . '' The investigation is `` being done as rapidly as we possibly can , '' he added . The D.C. Fire and Emergency Medical Services Department told CNN it is investigating the incident , which took place along the 1300 block of Rhode Island Avenue on Saturday . `` Our duty is to respond to all requests for emergency assistance . If it is determined that proper protocols were not followed at the conclusion of our investigation , then appropriate action will be taken , '' spokesman Tim Wilson said . The protocol is in question because , according to the Mills family , those who asked for help at the fire station were told to call 911 . Calls to 911 were placed , but a mix-up with the address delayed an ambulance , said Washington Council member Tommy Wells . `` Two things happened , '' he said . `` One was that no one came out of the fire house to help this gentleman . The other is the ambulance that was dispatched was dispatched to the wrong place . This was a number of fiascos . '' Paul Quander , deputy mayor for public safety , said a `` very new , probationary employee '' was at the facility . The employee 's first response should be `` to ask a senior person , and we believe that was done , '' he said , according to WTTG . `` The question now is what did that senior person say ? What did that person do ? Did they follow protocols and procedures ? '' There are no protocols that would prevent fire personnel from helping those in need , Quander told CNN Thursday . `` These are people who run into burning buildings . They work in the most hazardous conditions imaginable . `` They cross the streets , they cross highways to get to people . It is understood . It is common . This is why it is so troubling that we did not take the appropriate action in this case . It 's right across the street . '' `` It 's hard to get your arms around '' the idea that this took place , he added . Lt. Kellene Davis was the officer in charge of the station at the time of the incident , WTTG reports . Davis did not respond immediately to an e-mail Thursday from CNN , and a call to a phone number listed for her was not answered . Also Thursday , a spokesman said that two employees of the D.C. Fire and Emergency Medical Services Department have been suspended with pay in the wake of the incident . `` I can not say who they were because it is a personnel matter and an ongoing investigation , but I can tell you that neither of them was the probationary firefighter involved in the incident , '' said Keith St. Clair , with the office of the deputy mayor for public safety . The employees were working at the station , he said . Cecil Mills , a lifelong Washington resident , worked for the Department of Parks and Recreation . His daughter , in mourning , had kind words for the mayor 's handling of the matter . `` I appreciate how seriously he is taking this because it never should have happened , '' she told WTTG . Marie Mills was n't immediately available Thursday when contacted by CNN . The firefighters ' union said the incident simply should never have happened . `` We need to find out why it did occur and make sure it never happens again , '' said Ed Smith , president of the DC Fire Fighters Association , in a statement reported by WTTG . He added that on the union 's behalf , `` I offer Mr. Mills ' family a sincere apology . '' CNN 's Aaron Cooper and Mike M. Ahlers contributed to this report from Washington .
NEW : Two employees have been suspended with pay , a spokesman says . Three people tried to summon firefighters to help the collapsed man . Mills ' daughter said she saw a firefighter at the station . The fire department is investigating what caused the collapse and whether it was an accident or sabotage by someone else.