Date: 201507
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B757 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Second aircraft: A320
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction; Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; Flight Crew Took Evasive Action; General Physical Injury / Incapacitation
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: We had pushed off of gate. After calling for taxi; ground control instructed us to taxi to runway via X; Y; behind another air carrier. I read back the instructions. The controller then issued new instructions. We were to taxi to [runway] via Z; A; Y; behind the other aircraft. I read back the instructions and the Captain then verified the instructions by repeating them to me. We started to taxi via Z. I then saw that the Aircraft Y had turned onto taxiway X heading east toward us. The distance from taxiway Y to Z on X is rather short. I became concerned that perhaps the Captain hadn't noticed the other aircraft had turned onto taxiway X. I told him we had to stop for the Aircraft Y. Due to the timing and short distance involved an abrupt stop was necessary to avoid encroaching onto the taxiway in front of the other aircraft. After the stop I called the cabin to see if the flight attendants were okay. The flight attendant I spoke with informed me that she was injured and that she believed all the flight attendants were injured. I asked if they needed medical assistance and she said yes. I informed ground we had possible injuries and needed to return to the gate. I then called operations to inform them of our return and to have medical assistance dispatched to meet us. We returned to gate where the flight attendants were taken to receive treatment.


Second narrative: Taxiing from gate Ground Control instructed taxi X; Y [to] runway behind Aircraft Y. We saw traffic on Y abeam us and as we turned to enter Z Ground stated to taxi Z; A; Y [to] runway behind Aircraft Y. During all this time we assumed traffic was taxiing to [runway.] As I was eyes left to look for traffic on X and A and then centering slightly nose right about 1230; FO stated are you stopping for the other aircraft. I was stunned the traffic was there on X immediately stopped. Ground speed was 3-10 knots which resulted in injured person and galley noises. FA called to say there's 4 injured FAs and we need to return to the gate and have paramedics meet the plane. We returned to the gate and called for paramedics. Four FAs and one passenger were injured and sent to the hospital; eventually being released. I called the appropriate people and company for assistance.


Synopsis: A taxiing B757 Captain did not see an aircraft which they were cleared to follow. After the First Officer pointed out the developing conflict with it; he executed an emergency stop which injured four flight attendants and one passenger.